Pentagon Chief Ash Carter says Donald Trump's plan for ISIS doesn't need to be secret

Defense Secretary Ash Carter, who has continually declined to comment on a hotly contested presidential race often centering on national security issues, dismissed on Monday President-elect Donald Trump's campaign trail criticism that U.S. plans to fight the Islamic State group must remain entirely secret.

"There are secret tactics involved there, but the fact we're going to Mosul and Raqqa is clear, since they're the two biggest cities," Carter said Monday morning while speaking at an event hosted by the Atlantic Council and 1776, a venture capital firm that supports tech startups.

When pressed, Carter said a centerpiece of the campaign must include broadcasting the U.S.-led coalition's intent to defeat the Islamic State group, also known as ISIL.

"It's important for ISIL to know, and ISIL everywhere else to know, that we intend to destroy them," Carter said, adding, "The inspiration factor around the world – that's why it's so important to destroy them around Iraq and Syria."

See Ash Carter during an important trip:

Carter is not expected to stay on in his role in the next administration.

In campaign rallies, interviews and debates, Trump repeatedly refused to offer any specifics on how he would defeat the Islamic State group, claiming that revealing any part of the strategy would give the enemy an advantage. He criticized President Barack Obama and the Pentagon for giving away its intentions in the days leading up to the ongoing campaigns to liberate Mosul in Iraq and Raqqa in Syria, which Trump claims allowed the extremist fighters holed up there to better prepare their defenses.

"Whatever happened to the element of surprise, okay?" Trump said at the third presidential debate in October, arguing the administration wasted an opportunity to capture more Islamic State group leaders by broadcasting its intention to move on Mosul. "These people have all left. They've all left. The element of surprise. Douglas MacArthur, George Patton spinning in their graves at the stupidity of our country."

In his first interview since winning the election, Trump continued to decline offering specifics to 60 Minutes' Leslie Stahl.

"I'm not like the people going in right now and fighting Mosul and they announced it four months before they went into Mosul and everybody now is – it's a tough fight because, No. 1, the leaders of ISIS have left. Why do I have to tell you that?" Trump said in the interview which aired Sunday night. "I'm not going to say anything. I don't want to tell them anything. I don't want to tell anybody anything."

The Defense Department has struggled with keeping the details of its plans secret while also fulfilling its own pledge to remain transparent about its activities abroad. Officials from Central Command, the headquarters overseeing wars in the Middle East, came under criticism early last year for announcing the offensive to liberate Mosul would begin within months. The actual campaign was stalled by a shortage of organized and trained fighters in Iraq, as well as internal political disputes over which ethnic elements of the country's security forces would be involved in the liberation effort, and how.

Trump has argued his strategy in Iraq would include seizing its oil infrastructure to recoup the costs of war – a strategy experts believe is illegal, and would require and endanger tens of thousands of U.S. troops.

Carter said Monday that Trump's transition team had not yet arrived at the Pentagon to begin preparing for taking over the White House, though he expected those meetings to begin this week. Analysts at Defense have been providing detailed briefings to both candidates throughout the campaign.

Trump has not yet indicated who might succeed Carter, though rumors have circulated fellow Republicans Sen. Jeff Sessions of Georgia or Sen. Kelly Ayotte of New Hampshire, both members of the Senate Armed Services Committee, could take up the post. Retired Army Lt. Gen. Mike Flynn, formerly the head of the Defense Intelligence Agency and close adviser to the Trump campaign, would not qualify for the job according to current rules because he has not been out of uniform for the requisite seven years, though Flynn could get a congressional waiver.

Related: See more photos from the battle to reclaim Mosul:

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