Story highlights Russian meddling in the 2016 election is the subject of numerous investigations in Washington

Trump also slammed American media, particularly CNN and NBC

Warsaw, Poland (CNN) President Donald Trump said Thursday that he thinks Russia was behind 2016 election meddling, but added that he feels "it could have been other people in other countries" and that "nobody really knows for sure."

"I think it very well could be Russia but I think it could very well have been other countries," Trump said during a news conference with Polish President Andrzej Duda in which he also slammed the news media, including CNN and NBC. "I think a lot of people interfere."

Trump, asked about the fact the United States intelligence community has said it was Russia, compared that assessment to the eventually debunked claim that Iraq had weapons of mass destruction in the lead-up to the Iraq War.

"I think it was Russia but I think it was probably other people and or countries. I see nothing wrong with that statement," Trump said. "Nobody really knows. Nobody really knows for sure."

He added, "I remember when I was sitting back listening about Iraq, weapons of mass destruction, how everybody was 100% certain that Iraq has weapons of mass destruction. Guess what? That led to one big mess. They were wrong and it led to a mess."

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