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Jimmy Carter suggests Trump is an illegitimate president

Washington(CNN) Former President Jimmy Carter suggested Friday that a full investigation into Russian interference in the 2016 election would show that Donald Trump didn't win the presidency.

"There's no doubt that the Russians did interfere in the election. And I think the interference, although not yet quantified, if fully investigated would show that Trump didn't actually win the election in 2016. He lost the election and he was put into office because the Russians interfered on his behalf," Carter said at the Carter Center's retreat in Leesburg, Virginia.

Asked if he believes Trump is an illegitimate president, Carter paused for a moment.

"Based on what I just said, which I can't retract," Carter said to audience laughter.

Special counsel Robert Mueller's report found that Russia waged a "sweeping and systematic" influence campaign during the 2016 election with the goal of electing Trump, but did not establish a conspiracy between Trump's campaign and Moscow.

Trump was asked to react to Carter during a Saturday news conference in Osaka, Japan.

He said Carter is a Democrat and repeating a "typical talking point." Trump called Carter a "nice man, terrible president."

Trump defended his 2016 win, saying he "worked harder and worked smarter" than Hillary Clinton.

Until now, the former one-term Democratic president had shared a warmer relationship with the current President more than Trump has had with any other living president.

Though he has been critical of Trump's foreign policy and accused him of deepening racial divisions, Carter has also shown a willingness to help Trump.

He took a phone call from Trump in April -- the first time the two had spoken -- to discuss US-China trade negotiations.

Carter also offered to travel to North Korea in order to meet with Kim Jong Un on Trump's behalf, according to a Democratic US lawmaker.

In 2017, Carter told The New York Times that the media was "harder on Trump than any other president certainly that I've known about."

CNN's Betsy Klein contributed to this report.