Ukraine’s allies from Europe, Canada and Japan have voiced concerns over a US plan to end the Russia-Ukraine war, saying it “will require additional work”.

They said in a statement the plan had elements “essential for a just and lasting peace”, but cited concerns over border changes and caps on Ukraine’s army.

Later on Saturday, US President Donald Trump said the draft plan was not his “final offer” for Ukraine. On Sunday, security officials from Britain, France, Germany, the US and Ukraine will meet in Geneva, Switzerland.

President Volodymyr Zelensky earlier warned Ukraine faced “one of the most difficult moments in our history” over US pressure to accept the plan seen as favourable to Moscow.

Trump has given Ukraine until 27 November to accept the 28-point plan, while Russia’s President Vladimir Putin said it could be the “basis” for a settlement.

When asked on Saturday whether the current draft plan was his final offer for Ukraine, Trump told reporters at the White House: “No, not my final offer.”

“One way or another we have to get it [the war] ended, so we’re working on it,” he added.

US Secretary of State Marco Rubio and special envoy Steve Witkoff will be among those taking part in talks in Geneva on Sunday. National Security Adviser Jonathan Powell will attend on the UK’s behalf.

Saturday’s joint statement at the G20 summit in South Africa was signed by the leaders of Canada, Finland, France, Ireland, Italy, Japan, the Netherlands, Spain, the UK, Germany and Norway. Two top EU officials were also among the signatories.

The statement said: “We believe therefore that the draft is a basis which will require additional work. We are ready to engage in order to ensure that a future peace is sustainable. We are clear on the principle that borders must not be changed by force.

“We are also concerned by the proposed limitations on Ukraine’s armed forces, which would leave Ukraine vulnerable to future attack.”

It added: “The implementation of elements relating to the European Union and relating to Nato would need the consent of EU and Nato members respectively”.

UK Prime Minister Sir Keir Starmer, who is at the G20 summit in Johannesburg, spoke to Zelensky on the phone on Saturday, followed by a call with Trump.

On the Trump call, a Downing Street spokesman said Sir Keir “relayed the discussions that have been taking place between Coalition of the Willing partners [Ukraine’s allies] in attendance at the G20 summit today”.

They added: “The leaders agreed their teams would work together on the 28-point US peace proposal in Geneva tomorrow. They agreed to speak again tomorrow.”

Sir Keir earlier said he was concerned about proposed caps on Ukraine’s military in the US plan, saying “it’s fundamental that Ukraine has to be able to defend itself if there’s a ceasefire”.

The widely leaked US peace plan proposes Ukrainian troops withdraw from the part of the eastern Donetsk region that they currently control, and de facto Russian control of Donetsk, as well as the neighbouring Luhansk region and the southern Crimea peninsula annexed by Russia in 2014.

The plan also includes freezing the borders of Ukraine’s southern Kherson and Zaporizhzhia regions along the current battle lines. Both regions are partially occupied by Russia.

The US draft would also limit Ukraine’s military to 600,000 personnel, with European fighter jets stationed in neighbouring Poland.

Kyiv would receive “reliable security guarantees”, the plan says, although no details have been given. The document says “it is expected” that Russia will not invade its neighbours and Nato will not expand further.

The plan also suggests Russia will be “reintegrated into the global economy”, through the lifting of sanctions and by inviting Russia to rejoin the G7 group of the world’s most powerful countries – making it the G8 again.

On Friday, Trump said Zelensky would “have to like” the US proposals, adding otherwise Ukraine and Russia would continue fighting.

Earlier in the day, the Ukrainian leader addressed the nation with a stark warning that the country “might face a very difficult choice: either losing dignity, or risk losing a key partner”.

“Today is one of the most difficult moments in our history,” Zelensky added, pledging to work “constructively” with the Americans on the plan.

On Saturday, Zelensky announced that his head of office Andriy Yermak would lead Ukraine’s negotiating team for future talks on a peace deal, including any that may involve Russia.

“Our representatives know how to defend Ukraine’s national interests and exactly what must be done to prevent Russia from launching a third invasion, another strike against Ukraine,” the president said in a video statement posted on social media.

Kyiv is critically dependent on deliveries of US-made advanced weaponry, including air defence systems to repel deadly Russian air assaults, as well as intelligence provided by Washington.

Putin on Friday confirmed Moscow had received the US plan – but said it had not been discussed with the Kremlin in detail.

He added Moscow was willing to “show flexibility” – but was also prepared to fight on.

Putin launched a full-scale invasion of Ukraine in February 2022.

In recent months, Russian troops have been slowly advancing in Ukraine’s south-eastern region – despite reported heavy combat casualties.