Weston, Massachusetts - President Joe Biden said Tuesday he was unsure if he would be seeking reelection next year were Republican rival Donald Trump not also trying for a second term.

"If Trump wasn't running, I'm not sure I'd be running. But we cannot let him win," the 81-year-old Democrat told a 2024 election campaign fundraiser in Weston, Massachusetts.

Biden praised the "powerful voice" of former Republican lawmaker Liz Cheney who warned on Sunday that the United States would be "sleepwalking into dictatorship" if twice-impeached former president Trump returns.

He also mentioned the Atlantic magazine outlining what it said were the threats posed by a second Trump term, one of three major US media outlets to issue similar warnings in recent days along with the Washington Post and New York Times.

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During an earlier fundraiser in Boston, Biden cited Trump's increasingly extreme language on the campaign trail, including calling his opponents "vermin." Biden said that echoed the language used in Germany in the 1930s when Adolf Hitler's Nazis were on the rise.

"Trump's not even hiding the ball anymore. He's telling us what he's going to do," Biden said. "He's making no bones about it."

The Democrat, who beat Trump in 2020, an election that Trump still refuses to accept, has repeatedly portrayed himself as defending American democracy in next year's vote.

Trump, however, is narrowly ahead in opinion polls despite facing a number of criminal trials including one for election subversion.

Biden's age is a particular concern with voters and there have been calls from some Democrats for him to step aside for a new candidate. Many young voters and voters of color are turning away from the president for his spotty record on climate action and full-throated support for Israel's war on Gaza.

"Joe Biden is the real dictator," Trump responded in a post on Truth Social on Tuesday.