"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."
The intelligence community assessment spans both Obama and Trump administrations, however. Intelligence officials nominated by Trump have publicly said they have no doubt that Russia was behind the election meddling.
Russian meddling in the 2016 election is the subject of numerous investigations in Washington, casting a pall over the White House. The swirl of Russia investigations -- and possible connections between Trump's orbit and Russian officials -- has caused friction on Capitol Hill, hampering Trump's ability to score a number of legislative victories.
Trump slammed former President Barack Obama's handling of Russian interference as he stood next to Duda, arguing that the former president "did nothing" to combat the interference.
"Why did he do nothing about it? He was told it was Russia by the CIA ... and he did nothing about it," Trump said. "They said he choked. I don't think he choked. Well, I don't think he choked. I think what happened was he thought Hillary Clinton was going to win the election and he said let's not do anything about it. Had he thought the other way, he would have done something about it."
Obama confronted Russian President Vladimir Putin over election meddling, though, during the 2016 G20 meeting in Hanghzhou, China. Photos of the meeting showed a stern Obama staring down Putin.
Obama later revealed that he told Putin "to cut it out" in his meddling in the 2016 election or "there were going to be serious consequences if he did not." The Obama administration also later expelled 35 Russian diplomats from the United States and shuttered Russian compounds in Maryland and New York.
Trump's comments come during the first day of his foreign trip to Poland and Germany, the second international trip of his presidency. Trump did not formally take questions from reporters on his first trip, so the bilateral press conference with Duda on Thursday was Trump's first official conversation with reporters on foreign soil.
Attacks news coverage
Trump, standing next to Duda, also slammed American media, particularly CNN and NBC.
Trump, as he has done many times before, criticized CNN as "fake news" after being asked about CNN's coverage by David Martosko of the Daily Mail.
Trump's critique -- which came during his first formal press conference in nearly a month -- came in response to CNN's coverage of the video the President tweeted that showed him body-slamming a man with the CNN logo over his head.
"I think what CNN did was unfortunate for them. As you know, they now have some pretty serious problems. They have been fake news for a long time. They have been covering me in a very dishonest way," Trump said.
Martosko met with Trump to pitch him the idea of writing a book about the President, CNN has reported
. Numerous reports have also indicated that the reporter was considered for a press job in the White House. Martosko later tweeted a statement pulling him out of consideration for any White House job.
"Since you started the whole wrestling video thing, what are your thoughts about what has happened since then? CNN went after you and has threatened to expose the identity of a person," Martosko asked before being cut off by Trump.
CNN did not threaten to expose the identity of anyone behind the video, but did contact the Reddit user who originally posted the video that Trump tweeted.
A spokesman for the news network said CNN decided not to publish the name of the Reddit user out of concern for his safety and that "any assertion that the network blackmailed or coerced him is false." The user, who had a long history of posting anti-semitic, racist and anti-Muslim content, apologized for his posts after being contacted by CNN but before speaking to the network.
Martosko was standing directly behind a number of smiling Trump aides when he asked the question. Martosko shook hands with Dan Scavino, Trump's director of social media, after the news conference.
After slamming CNN as fake news, Trump turned to Duda and asked, "Do you have that also, Mr. President?"
Duda has been accused of curbing press freedoms in Poland. Though he denies the criticisms, the fears of curbs being put on reporters have led to protests throughout the country.
CORRECTION: This story has been updated to more accurately reflect Trump's comments. He said "nobody" instead of "no one" with regard to who "knows for sure" about Russian meddling in the election.