President Trump says 'Nobody really knows' if Russia interfered in 2016 election

President Trump on Thursday said that "nobody really knows" whether Russia hacked the 2016 presidential election -- a statement that comes one day before the U.S. commander in chief is set to meet Vladimir Putin face-to-face at the G20 summit in Hamburg.

During a joint press conference with Polish President Andrzej Duda, Hallie Jackson of NBC News asked the U.S. president whether he would "definitively say that Russia interfered in the 2016 election."

"Well I think it was Russia and I think it could have been other countries," Trump said in response. "I think a lot of people interfere. I think its been happening for a long time. It's been happening for many, many years."

Watch below for Trump's full response on Russia's 2016 election involvement:​​​​​​

The president continued, suggesting there is no definitive answer as to whether Russia was involved in a hack of the 2016 election.

"Mistakes have been made. I agree, I think it was Russia, but I think it was other people and countries, and I see nothing wrong with that statement," Trump said. "Nobody really knows. Nobody really knows for sure."

The FBI, NSA and CIA were all involved in an assessment that produced the intelligence agreement that Russia interfered in the 2016 election. This was confirmed during congressional testimony offered by former Director of National Intelligence James Clapper on May 8.

Trump then pivoted, though, and slammed former President Barack Obama for what he described as intentional inaction on the CIA intelligence that Russia was interfering in the 2016 contest between Democratic candidate Hillary Clinton and then-Republican candidate Donald Trump.

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"The thing I have to mention is that Barack Obama, when he was president, found out about this ... in August. Now, the election was in November," Trump said. "That's a lot of time. He did nothing about it. He was told it was Russia by the CIA, and he did nothing about it."

Trump has been preparing for his scheduled "sideline" meeting with Putin -- an exchange the Kremlin hopes will foster a dialogue between the two nations. According to a New York Times report, top Trump aides are worried about what their boss might say to the Russian president.

Trump wrapped up his remarks on the 2016 election by comparing giving a definitive answer on the matter to the reports that Iraq had weapons of mass destruction during the Iraq war.

"I remember when I was sitting back listening about Iraq,' Trump said. "Weapons of mass destruction, how everyone was 100 percent sure it was weapons of mass destruction. Guess what? That led to one big mess."