Former White House adviser Susan Rice criticized former President Trump over his foreign policy agenda, calling him an "appeaser" and likening him to former British Prime Minister Neville Chamberlain — who tried to appease Nazi leader Adolf Hitler.

"The fundamentals of national security — that America needs to be strong, that we need to stand with our allies, we need to stand for our values, we have to mean what we say," Rice, who served under the Obama administration, said in an interview Thursday with MSNBC's Lawrence O'Donnell. "These are very fundamental things that never used to be under serious question."

"And along comes Donald Trump, who really is like the Neville Chamberlain of the Republican Party," she added.

Rice also called Trump a "surrender monkey" and referred to the former president's rhetoric about Ukraine and its nearly three-year war with Russia.

Trump and Ukrainian President Volodymyr Zelensky have a rocky past, including a phone call that led to his first impeachment in 2019. During the incident, then-President Trump pressured Zelensky to open an investigation into Joe Biden and his son, Hunter Biden, in exchange for releasing about $400 million in military aid.

"He's an appeaser, he's a surrender monkey, and that's what we're seeing in his approach to Ukraine," Rice said.

Trump, after meeting with the Ukrainian leader last week, lauded his relationship with Zelensky and Russian President Vladimir Putin, suggesting he could broker an end to the war "very quickly," and that would work out for both sides.

Rice added that she has seen Trump "fold to [Chinese President] Xi Jinping and many others."

Trump has been less committal than Biden to helping Taiwan fend off potential Chinese military aggression. However, Trump and his top foreign policy advisers threatened earlier this year to enact more aggressive policies toward China if the GOP presidential nominee is elected in November.

In the interview, Rice also talked about the letter she and more than 700 other bipartisan national security leaders signed onto, endorsing Vice President Harris following Biden's decision to withdraw from the race.

"That is why more than 700 Democrats, Republicans and independents, very senior national security leaders, came together to oppose Donald Trump and support Kamala Harris," Rice said, adding that the vice president has the "temperament" and "experience" to be an "effective" commander in chief.

The Hill has contacted the Trump campaign for comment.