“It could very well have been Russia, but I think it could well have been other countries.”

With one more day to go before his first face-to-face meeting with Russian President Vladimir Putin, President Donald Trump on Thursday once again cast doubt on US intelligence agencies’ assessment that Russia interfered in the 2016 US presidential election.

“Well, I think it was Russia, and I think it could have been other people in other countries,” Trump said at a press conference in Warsaw with Polish President Andrzej Duda. “It could have been a lot of people interfered.” (Trump has previously suggested China or “some 400 pound guy” could also be responsible for hacking into email accounts of Democratic officials.)

Trump then seemed to backtrack, suggesting that the intelligence was uncertain: “I think it could very well have been Russia, but I think it could well have been other countries, and I won’t be specific, but I think a lot of people interfere.” Trump added that President Barack Obama “found out about this—in terms of, if it were Russia—found out about it in August.” Trump proceeded to blame Obama for not responding effectively to the interference.

After a reporter pointed out that US intelligence agencies have been “far more definitive” than Trump in declaring that Russia interfered in the election, Trump sought to cast doubt on that intelligence. He emphasized that the intelligence assessment was produced by just “three or four” of the country’s 17 intelligence agencies.

“I agree,” Trump added. “I think it was Russia, but I think it was probably other people and/or countries, and I see nothing wrong with that statement. Nobody really knows. Nobody really knows for sure.”

Trump then invoked past US intelligence failures, saying that “everybody was 100 percent sure that Iraq had weapons of mass destruction. Guess what: That led to one big mess. They were wrong.”

“So it was Russia, and I think it was probably others also, and that’s been going on for a long period of time,” added Trump.

Despite the evidence pointing to Russian hacking, as well as bipartisan acknowledgement that the Kremlin actively worked to undermine Hillary Clinton, White House officials have indicated Trump is unlikely to broach the subject during his meeting with Putin Friday.