Getty ImagesGermany's defence minister has warned Ukraine not to agree to a deal which involves sweeping territorial concessions in return for a ceasefire with Russia.
Boris Pistorius said Ukraine "should not go as far as the latest proposal by the American president", which he said would amount to a "capitulation".
US President Donald Trump said this week that "most of the major points [of the deal] are agreed to". Reports suggest that Ukraine could be asked to give up large portions of land seized by Russia, including Crimea.
Ukrainian President Volodymyr Zelensky has repeatedly rejected territorial concessions, saying issues about land can be discussed once a ceasefire has been agreed.
On Sunday, Pistorius told German public broadcaster ARD that Kyiv knew that it might have to part with some territory to secure a ceasefire.
"But they will certainly not go as far - or should not go as far - as the latest proposal by the American president," he said.
"Ukraine could have got a year ago what was included in that proposal, it is akin to a capitulation. I cannot discern any added value."
The BBC has not seen the exact details of the latest US plan. On Friday, Reuters news agency reported that it had seen proposals from the US that included American legal acceptance of Russia's illegal annexation of Crimea and de facto recognition of Russian control of other occupied areas, including all of Luhansk in the east of the country.
Reuters says it has also seen a counter-proposals from Europe and Ukraine, which reportedly say the sides will only discuss what happens to occupied Ukrainian territory once a ceasefire has come into effect.
The US plan also rules out Ukraine's membership in the Nato military alliance and sees a UK-France led "coalition of the willing" providing a security guarantee once a ceasefire is in force without the involvement of the US.
Meanwhile the Europeans want the US to give "robust" guarantees in the form of a cast-iron Nato-style commitment to come to Ukraine's aid if it is attacked.
The US reportedly further proposes to take control of the Zaporizhzhia nuclear plant - currently occupied by Russia - which would then provide electricity to both Russia and Ukraine. The counter-plan makes no mention of giving Russia power.
In an interview with Time magazine this week, Trump once again blamed Kyiv for starting the war, citing its ambitions of joining Nato.
The US president also told Time: "Crimea will stay with Russia."
On Sunday, US Secretary of State Marco Rubio urged Russia and Ukraine to move forward to secure a peace deal.
"It needs to happen soon," Rubio told NBC. "We cannot continue to dedicate time and resources to this effort if it's not going to come to fruition."
The US has recently warned it would walk away from negotiations if progress was not made.
It follows a one-on-one meeting between Zelensky and Trump at the Vatican on the sidelines of the Pope's funeral on Saturday.
The White House described the meeting as "very productive" while the Ukrainian president said it had the "potential to become historic".
Russia launched a full-scale invasion of Ukraine in 2022, and Moscow currently controls almost 20% of Ukrainian territory.
