President Donald Trump at a news conference with Polish President Andrzej Duda at the Royal Castle on Thursday. Associated Press/Evan Vucci

A Kremlin spokesman seized Thursday on comments from President Donald Trump that appeared doubtful of US intelligence findings that Russia interfered in the 2016 presidential election.

The spokesman, Dmitry Petrov told Bloomberg News that Trump had highlighted "equally the possibility that it could have been other countries.

"Please note the nuances," he said.

Trump's comments, made earlier Thursday at a joint news conference in Warsaw, Poland, alongside Polish President Andrzej Duda, had appeared to undercut the conclusion reached by several US intelligence agencies that Russia was to blame. Russia has consistently denied meddling in last year's election.

"I think it was Russia, but I think it was probably other people and/or countries," Trump told reporters. "Nobody really knows. Nobody really knows for sure."

"Everybody was 100% sure that Iraq had weapons of mass destruction," he added. "Guess what? That led to one big mess. They were wrong, and it led to a mess."

Trump instead cast blame on President Barack Obama, who he said did not act aggressively enough to counter foreign interference.

"They say he choked. Well, I don't think he choked," Trump said. "I think he thought Hillary Clinton was going to win the election, and he said, 'Let's not do anything about it.'"

Trump is set to meet Russian President Vladimir Putin in person for the first time as president Friday, but the White House has said there's "no specific agenda" for their discussion.