Polish Prime Minister Donald Tusk said “it would be good to know for sure who is the author of the plan,” as tensions over elements that mirror long-standing Russian demands.

Secretary of State Marco Rubio rejected the claims, writing on social media that "the peace proposal was authored by the U.S."

GOP Rep. McCaul said Sunday he would advise against Ukraine signing the peace proposal that President Donald Trump has offered to end its war with Russia.

The president also took aim at former President Joe Biden, arguing that Putin only attacked Ukraine because Biden was president at the time.

Secretary of State Marco Rubio said Sunday that talks between the United States and Ukraine in Switzerland have been the "most productive and meaningful so far," as European leaders questioned the peace plan.

Three U.S. senators said Saturday that Secretary of State Marco Rubio told them President Donald Trump' s Ukraine peace plan is a Russian "wish list" and not the administration's actual proposal.

The gathering in South Africa comes as US President Donald Trump gives Ukraine until Thursday to agree to the deal.

U.S., Ukrainian and European officials gathered in Switzerland on Sunday for talks on the contentious American-Russian peace plan put to Kyiv this week.