The United States and its negotiating partners agreed "in secret" to allow Iran to evade some restrictions in last year's landmark nuclear agreement in order to meet the deadline for it to start getting relief from economic sanctions, according to a report reviewed by Reuters.
The report is to be published on Thursday by the Washington-based Institute for Science and International Security, said the think tank's president David Albright, a former U.N. weapons inspector and co-author of the report. It is based on information provided by several officials of governments involved in the negotiations, who Albright declined to identify.
RELATED: United States and Iran Relations throughout time
United States and Iran Relations throughout time
United States and Iran Relations throughout time
Two lines of troops loyal to Ayatollah Ruhollah Khomeini stand in front of the U.S. Embassy during shooting in the compound, Feb. 15, 1979 in Tehran. (AP Photo)
In this Nov. 9, 1979, file photo, one of the hostages being held at the U.S. Embassy in Tehran is displayed blindfolded and with his hands bound to the crowd outside the embassy. The U.S. and Iran cut off diplomatic ties in 1979 after the Islamic Revolution and the storming of the U.S. Embassy in Tehran, where 52 Americans were held hostage for more than a year. Since his inauguration in 2009, President Barack Obama has expressed a willingness to meet with the Iranians without conditions. The U.S. and Iran secretly engaged in high-level, face-to-face talks, at least three times over the past year, in a high stakes diplomatic gamble by the administration that paved the way for the historic deal aimed at slowing Iran's nuclear program. (AP Photo/File)
President Carter faces reporters at the White House as he announces the U.S. will seek economic sanctions against Iran, Dec. 21, 1979 in Washington. Secretary of State cyrus Vance looks on. Vance died Saturday, Jan. 12, 2002. He was 84. Appointed secretary of state by Jimmy Carter in 1977, Vance promoted reconciliation with Russia, human rights as a pillar of American foreign policy, normalization of relations with China and, above all, diplomacy as the alternative to using force. (AP Photo)
This is the entrance to the U.S. Embassy in Tehran, Iran where 63 people are being held hostage, seen in 1980. Graffiti on the wall at left reads: "Dear American minority, brothers and sisters (Blacks and Indians) study the holy Koran and start a revolution against U.S. discrimination. God and Iranian Muslim people are supporting you. Down with Reagan." (AP Photo)
Return of the hostages from Iran as they step off the plane in Germany. Barry Rosen is second from the bottom waving with no glasses and a beard. He has just announced that he will be going back to Iran to meet with his captors. The hostages were kept over a year in captivity after the US Embassy was stormed during the Iranian Revolution. Relations with Iran and the US have been improving lately. (photo by Tim Chapman)
A Kurdish family having fled northern Iraq, carry all their worldly possessions, reach the border town of Nossod, Iran. Saddam Hussein crushed the Kurdish uprising in northern Iraq in the aftermath of 1991 Gulf War led by the US and allied forces. (Photo by Kaveh Kazemi/Getty Images)
Iranian President Mohammad Khatami, greets thousands of students during his speech at a university stadium in Tehran, Iran Sunday, Dec. 12, 1999. The stadium erupted in cheers when Khatami declared that his nation felt no enmity toward the American people. Iran-U.S. ties have been strained since Washington severed ties over the 1979 storming of the U.S. Embassy in Tehran by Islamic militants. Relations thawed after the May 1997 election of Khatami. (AP Photo/Hasan Sarbakhshian)
An Iranian woman pets a dove caged in the belly of a replica of the Statue of Liberty at the former US embassy compound November 3, 2001 in Tehran, Iran. Iranian authorities opened the former embassy to the public for the first time since the 1979 Islamic revolution toppled the US-backed Shah which ultimately led to the breaking of relations between Washington and Tehran. (Photo by Keivan/Getty Images)
Reza Pahlavi, son of the late Shah of Iran Mohammad Reza Shah Pahlavi, speaks to New York University students December 4, 2001 in New York City. Pahlavi spoke of the need to root out terrorism and the need for democracy in Iran. (Photo by Mario Tama/Getty Images)
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Deputy Secretary of State Richard Armitage greets people before giving testimony before the U.S. Senate Foreign Relations Committee on Capitol Hill October 28, 2003 in Washington DC. The Committee is hearing testimony on security threats and the U.S. policy toward Iran. (Photo by Mark Wilson/Getty Images)
An Iranian girl rests during a meeting of the conservative group, the Coalition of Builders of Islamic Iran, in Tehran February 16, 2004. The group has taken a tough stance on the country's nuclear prerogatives and a moderate line on US-Iranian relations and the imposition of Islamic social regulations. The main reformist parties are staying away after a conservative-run political vetting body, the Guardians Council, barred some 2,300 people -- most of them reformists -- from even standing in the February 20 polls. (Photo credit: BEHROUZ MEHRI/AFP/Getty Images)
A man holds an effigy of U.S. President George W. Bush during a protest against the U.S.-led occupation of Iraq in Enqelab Square May 19, 2004 in Tehran, Iran. Demonstrators reportedly hurled petrol bombs, firecrackers and stones at the British embassy. (Photo by Majid/Getty Images)
This 18 January file photo shows Secretary of State-designate Condoleezza Rice testifying before the Senate Foreign Relations Committee during her confirmation hearing on Capitol Hill in Washington, DC. US Secretary of State Condoleezza Rice will discuss the war in Iraq and tensions with Iran when she meets Chancellor Gerhard Schroeder on 04 February 2005.(Photo credit: TIM SLOAN/AFP/Getty Images)
U.S. Senator Dick Lugar (R-IN) (C) speaks to the media after addressing the U.N. Security Council at the United Nations February 6, 2006 in New York City. Lugar, along with other Senate Foreign Relations Committee members George Voinovich (R-OH) (R) and Norm Coleman (R-MN), spoke on reform at the U.N., Iran and energy conservation. (Photo by Spencer Platt/Getty Images)
Iranian Foreign Minister Manouchehr Mottaki speaks during a meeting with relatives of the seven Iranian detainees arrested in Iraq by US forces, in Tehran, 18 May 2007. US troops seized seven Iranians in the northern Iraqi city of Arbil on 11 January from what Iran claims was an official consular building. Mottaki said after meeting the families of the detainees that Iran maintains that they were diplomats working for a 'consulate'. (Photo credit: ATTA KENARE/AFP/Getty Images)
Iranian students walk past an anti-US mural on the wall of the former US embassy in Tehran 24 October 2007. Twenty-eight years ago, 19-year-old Iranian chemistry student Massoumeh Ebtekar agreed to join other students in holding more than 60 Americans captive at their embassy in Tehran, an event that was to last 444 days and leave a rupture in US-Iranian relations that has yet to be healed. For Ebtekar, who was elected last year as a member of Tehran city council, there is no contradiction between her prominent role in the embassy siege and her efforts today for greater moderation in the Islamic republic. (Photo credit: ATTA KENARE/AFP/Getty Images)
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Holding an anti-Bush poster and pictures of Iranian late revolutionary founder Ayatollah Khomeini, left on the posters, and supreme leader Ayatollah Ali Khamenei, right on the posters, Iranians attend a demonstration in front of the former U.S Embassy in Tehran, Iran, Sunday, Nov. 4, 2007, in a ceremony commemorating the 28th anniversary of the seizure of the U.S. Embassy by militant students on Nov. 4, 1979. (AP Photo/Vahid Salemi)
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Reuters could not independently verify the report's assertions.
"The exemptions or loopholes are happening in secret, and it appears that they favor Iran," Albright said.
Among the exemptions were two that allowed Iran to exceed the deal's limits on how much low-enriched uranium (LEU) it can keep in its nuclear facilities, the report said. LEU can be purified into highly enriched, weapons-grade uranium.
The exemptions, the report said, were approved by the joint commission the deal created to oversee implementation of the accord. The commission is comprised of the United States and its negotiating partners -- called the P5+1 -- and Iran.
One senior "knowledgeable" official was cited by the report as saying that if the joint commission had not acted to create these exemptions, some of Iran's nuclear facilities would not have been in compliance with the deal by Jan. 16, the deadline for the beginning of the lifting of sanctions.
The U.S. administration has said that the world powers that negotiated the accord -- the United States, Russia, China, Britain, France and Germany -- made no secret arrangements.
A White House official, speaking on condition of anonymity, said the joint commission and its role were "not secret." He did not address the report's assertions of exemptions.
Diplomats at the United Nations for the other P5+1 countries did not respond to Reuters' requests for comment on the report.
The report's assertions are likely to anger critics of the nuclear deal. Republican presidential candidate Donald Trump has vowed to renegotiate the agreement if he's elected, while Democrat Hillary Clinton supports the accord.
Albright said the exceptions risked setting precedents that Iran could use to seek additional waivers.
Albright served as an inspector with the U.N. International Atomic Energy Agency (IAEA) team that investigated former Iraqi President Saddam Hussein's nuclear weapons program.
While Albright has neither endorsed nor denounced the overall agreement, he has expressed concern over what he considers potential flaws in the nuclear deal, including the expiration of key limitations on Iran's nuclear work in 10-15 years.
EXEMPTIONS ON URANIUM, "HOT CELLS"
The administration of President Barack Obama informed Congress of the exemptions on Jan. 16, said the report. Albright said the exemptions, which have not been made public, were detailed in confidential documents sent to Capitol Hill that day -- after the exemptions had already been granted.
The White House official said the administration had briefed Congress "frequently and comprehensively" on the joint commission's work.
Democratic Senator Bob Menendez, a leading critic of the Iran deal and a senior member of the Senate Foreign Relations Committee, told Reuters in an email: "I was not aware nor did I receive any briefing (on the exemptions)."
As part of the concessions that allowed Iran to exceed uranium limits, the joint commission agreed to exempt unknown quantities of 3.5 percent LEU contained in liquid, solid and sludge wastes stored at Iranian nuclear facilities, according to the report. The agreement restricts Iran to stockpiling only 300 kg of 3.5 percent LEU.
The commission approved a second exemption for an unknown quantity of near 20 percent LEU in "lab contaminant" that was determined to be unrecoverable, the report said. The nuclear agreement requires Iran to fabricate all such LEU into research reactor fuel.
If the total amount of excess LEU Iran possesses is unknown, it is impossible to know how much weapons-grade uranium it could yield, experts said.
The draft report said the joint commission also agreed to allow Iran to keep operating 19 radiation containment chambers larger than the accord set. These so-called "hot cells" are used for handling radioactive material but can be "misused for secret, mostly small-scale plutonium separation efforts," said the report. Plutonium is another nuclear weapons fuel.
The deal allowed Iran to meet a 130-tonne limit on heavy water produced at its Arak facility by selling its excess stock on the open market. But with no buyer available, the joint commission helped Tehran meet the sanctions relief deadline by allowing it to send 50 tonnes of the material -- which can be used in nuclear weapons production -- to Oman, where it was stored under Iranian control, the report said.
The shipment to Oman of the heavy water that can be used in nuclear weapons production has already been reported. Albright's report made the new assertion that the joint committee had approved this concession.
(Reporting by Jonathan Landay; editing by John Walcott and Stuart Grudgings)