Former Vice President Joe Biden Joe BidenSenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies Biden says Ginsburg successor should be picked by candidate who wins on Nov. 3 MORE warned on Thursday that President Trump is leading the United States "down a very dark path," saying that the president's policies and rhetoric threaten to undermine the country's international standing.

Biden spoke at an event at Washington's Center for Strategic and International Studies in Washington where he received the Zbigniew Brzezinski Annual Prize. In his speech, Biden painted a grim picture of international relations that included the United States losing influence and credibility.

"We really worry that we're walking down a very dark path," Biden said. "It's not alarmist. We're walking down a very dark path that isolates the United States on the world stage and, as a consequence, endangers — not strengthens — endangers American interests and the American people."

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While the former vice president rarely mentioned Trump by name, he criticized the president's "appeal to populism and nationalism," warning that such forces would give way to global instability.

"The appeal to populism and nationalism is a siren song, a way for charlatans to aggrandize their power, raise themselves up, break down those mechanisms that are designed within our Constitution and internationally to limit the abuse of power and destabilize the world," he said.

In the wide-ranging speech, Biden touched on Trump's handling of North Korea, Iran and Russia.

Biden criticized the president's threat to "totally destroy" North Korea. Such rhetoric, Biden said, would only serve to escalate tensions between Washington and Pyongyang.

Biden also slammed Trump amid reports that he is planning to decertify Iran's compliance with the nuclear deal, an agreement brokered under the Obama administration that aims to curb Tehran's nuclear ambitions in exchange for sanctions relief. Doing so, Biden said, would damage Washington's credibility and would only serve to isolate the U.S.

Biden, 74, has maintained a relatively high profile since leaving office in January, increasing speculation that he could run for president in 2020.