Ukrainian President Volodymyr Zelensky will be coming into Monday’s White House meeting with President Donald Trump with a demand that could be a dealbreaker in terms of reaching any lasting peace arrangement with Russia.

Zelensky said Sunday that Kyiv will not surrender territory not currently occupied by Russian forces as part of any peace deal, adding that Ukraine’s constitution forbids it.

“We need real negotiations,” Zelensky said to reporters in Brussels at a press conference with European Commission President Ursula von der Leyen, per Just the News.

In addition to meeting with Trump, other European leaders are expected to be at the White House as well, reports said.

Zelensky stated that Russia has been unable to seize part of eastern Ukraine it has sought to control since 2014. He emphasized that Russian President Vladimir Putin “has been unable to take it for 12 years, and the constitution of Ukraine makes it impossible … to give up territory or trade land,” according to Politico.

While Trump is pushing for a formal peace deal, Secretary of State Marco Rubio said Sunday that a possible ceasefire between Russia and Ukraine is “not off the table,” as the U.S. continues to take part in negotiations aimed at ending the war.

“It was agreed to by all that the best way to end this conflict is through a full peace deal,” Rubio said during a “Meet the Press” interview on NBC News. “There’s no doubt about that. I mean, who would be against the fact that tomorrow we came to you and said, ‘We have a full peace deal, and it’s done.’ I think that’s the best way to end the war.”

Rubio said in the past that the U.S. had pushed for a ceasefire, but Russia has never agreed to one.

“We think usually it’s very hard to negotiate when you’re in the middle of hostilities,” Rubio said. “But that said, the only way to have a ceasefire is for both sides to agree to stop firing at one another … and the Russians just haven’t agreed to that.”

Rubio was then asked if he believed Trump issuing new sanctions on Russia would bring Moscow to the negotiating table and accept a ceasefire agreement.

“I don’t think new sanctions on Russia are going to force them to accept a ceasefire,” he said. “They’re already under very severe sanctions.”

Zelensky delivered the remarks on Sunday at a joint press conference with European Commission President Ursula von der Leyen, who is set to accompany him to Washington for talks with Trump on Monday, RT.com noted.

The Ukrainian leader said Moscow has put forward “many demands” regarding the conflict’s resolution and emphasized that Kyiv must be fully informed of them before moving forward.

Trump spoke with Zelensky and European leaders while aboard Air Force One returning home on Friday from his first face-to-face meeting with Putin since his first term, The Hill reported.

“It was determined by all that the best way to end the horrific war between Russia and Ukraine is to go directly to a Peace Agreement, which would end the war, and not a mere Ceasefire Agreement, which often times do not hold up,” Trump posted on Truth Social early Saturday.

Trump and Putin met at Elmendorf-Richardson Air Force Base in Alaska.

“President Zelenskyy will be coming to D.C., the Oval Office, on Monday afternoon. If all works out, we will then schedule a meeting with President Putin,” he added.

Zelensky signaled his support for a trilateral meeting between the three leaders in a post on X.

“President Trump informed about his meeting with the Russian leader and the main points of their discussion,” the Ukrainian leader wrote. “It is important that America’s strength has an impact on the development of the situation… I am grateful for the invitation,” he added.