Sen. Mark Warner (D-Va.) said Sunday morning that the Trump administration’s 28-point plan for peace between Russia and Ukraine “would go down, frankly, as a historically bad deal, rivaling Neville Chamberlain giving in to Hitler before World War II.

Warner, the highest ranking Democrat on the Intelligence Committee, told “Fox News Sunday” host Shannon Bream that he fears the plan could embolden Chinese leader Xi Jinping to pursue an invasion of Taiwan if accepted, blasting the proposal as “a total capitulation by Ukraine.”

“Clearly this plan was at least initially laid out as simply Russian input and no Ukrainian input,” Warner said. “Now they’re saying there has been Ukrainian input. Now the president is changing his mind again about whether this is a final offer or not. At the end of the day, we all want to see peace, but we don’t want to see a peace that rewards Vladimir Putin.”

The proposal, which was first reported by Axios, would see Ukraine cede the Donbas region to Russia, in addition to facing limits on the size of its military, per details of the plan obtained by POLITICO. Warner told Bream he’s not sure the deal is something Ukrainian President Volodymyr Zelenskyy “could even survive within his own government.”

The plan has attracted criticism from some of the GOP’s top Russia hawks, including Sens. Lindsey Graham (R-S.C.), Mitch McConnell (R-Ky.) and Roger Wicker (R-Miss.), who are pushing the Trump administration to rethink the proposal.

Still, the Trump administration enjoys the backing of many voices in the party, including Sen. Eric Schmitt (R-Mo.), who urged restraint from critics during a Sunday morning interview with Bream. Schmitt said key details of the plan, including security guarantees and territorial concessions, remain in flux.

“I think President Trump approaches this as a realist,” Schmitt said on Fox. “You take the world as it is, not how you want it to be, not how you wish it would be, but actually how it is. And the truth of the matter is — and a lot of people won’t say it — is the Ukrainians have been losing for a long time.”

Neither party in the war has publicly commented on the plan, although Ukrainian President Volodymyr Zelenskyy’s office said in a Thursday statement that it remains “ready now, as before, to work constructively with the American side, as well as with our partners in Europe and around the world so that the outcome is peace.” Ambassador to the United States Olga Stefanishyna was guarded in her remarks Sunday on CBS’ “Face the Nation,” telling host Margaret Brennan only that negotiations are ongoing and that the plan “is not about the justice” in Ukraine’s view.

Zelenskyy reiterated Sunday afternoon that “The crux of the entire diplomatic situation is that it was Russia, and only Russia, that started this war, and it is Russia, and only Russia, that has been refusing to end it throughout the full-scale invasion.”

He also urged all parties to seek a “dignified” peace “so that this war is truly ended and so that it does not happen again.”

Warner echoed his comments during a Sunday appearance on “This Week,” telling ABC’s Martha Raddatz that the plan “would make Neville Chamberlain’s giving in to Hitler outside of World War II look strong in comparison.”

British Prime Minister Chamberlain lauded the 1938 Munich agreement, which allowed for Germany to annex parts of Czechoslovakia, as “peace for our time,” but historians largely see the deal as a key turning point in laying the groundwork for Adolf Hitler’s invasion of Poland the following year.

White House press secretary Karoline Leavitt defended the proposal, telling POLITICO in a Thursday statement it “was crafted to reflect the realities of the situation, after years of a devastating war, to find the best win-win scenario, where both parties gain more than they must give.”

She also reiterated the Trump administration’s commitment to ensuring any truce deal includes security guarantees and deterrence measures in addition to opportunities for Ukraine to rebuild and for Russia to rejoin the global economy.

The proposal says that any future Russian attack on Ukrainian territory would be met with a “decisive, coordinated military response,” although it does not specify what such a response would entail. It also allows Ukraine to negotiate for membership in the European Union and calls for about $100 billion in frozen Russian assets and another $100 billion in European funds to be used for the rebuilding of Ukraine.

European officials have roundly lambasted the proposal, with security officials from Ukraine’s staunchest allies meeting for high-level talks to weigh in on the proposal. Top Trump administration officials were also set to meet with Zelenskyy’s advisers in Geneva on Sunday to iron out details of the plan, which Trump has given Ukraine until Thursday to sign on to.