President Volodymyr Zelensky warned on Friday that Ukraine risked losing its dignity and freedom - or Washington's backing - over a US peace plan that endorses key Russian demands, a proposal Donald Trump said Kyiv should accept within a week.

The US president told Fox News Radio he believed Thursday was an appropriate deadline for Kyiv to accept the plan.

Trump later told reporters that time was short given the approaching winter and need to end the bloodshed and that Zelensky would have to approve the plan.

"He'll have to like it, and if he doesn't like it, then you know, they should just keep fighting, I guess," he said.

Washington's 28-point plan calls on Ukraine to cede territory, accept limits to its military and renounce ambitions to join Nato. It also contains some proposals Moscow may object to and requires its forces to pull back from some areas they have captured, according to a draft seen by Reuters.

Russia's President Vladimir Putin, who has previously refused to budge on Russia's key territorial and security demands, said on Friday the US plan could be the basis of a final resolution of the nearly four-year-old conflict. He said Kyiv was against the plan but neither it nor its European allies understood the reality of Russian advances in Ukraine.

Zelensky, who has rejected the plan's terms in the past as capitulation, appealed to Ukrainians for unity and said he would never betray Ukraine. In public, Zelensky has appeared careful not to reject the US plan or offend the Americans.

He spoke on Friday with the leaders of Britain, Germany and France, and later with US Vice President JD Vance. He said he had agreed with Vance to have their advisers work "to find a workable path to peace".

The plan is expected to dominate discussions on the sidelines of the G20 summit in Johannesburg that European leaders are attending this weekend despite a boycott by Trump. The Europeans have not been consulted on the US plan and have expressed strong support for Kyiv. (Reuters)