Sir Keir Starmer and other European leaders have expressed 'concern' over Donald Trump's plan to end the war in Ukraine.

With the situation on a knife-edge, the Prime Minister and other European leaders – who had appeared blindsided by the proposals - began discussing alternatives on the sidelines of the G20 summit in Johannesburg on Saturday.

They said the proposal would 'require additional work' and expressed concerns about the proposal to limit Kyiv's armed forces.

In a joint statement issued following their meeting this afternoon, the leaders also stressed that 'borders must not be changed by force'.

Under the humiliating 28-point White House-Kremlin plan, Ukraine would cede territory its troops have defended since February 2022, slash the size of its military and sacrifice its sovereignty.

In return, sanctions against Russia would be lifted and, crucially for Vladimir Putin, the country would be 'reintegrated into the global economy'.

The Russian leader appears to have embraced the deal after saying he believes 'it can be used as the basis for a final peaceful settlement', while President Volodymyr Zelensky is seeking to propose alternatives.

Ukrainian envoys will meet a US delegation in Switzerland to discuss the proposal, Zelensky announced Saturday, after Trump set a deadline of less than a week to approve the deal.

National security advisors from the UK, France and Germany will also meet US and Ukrainian officials taking part in the talks in Geneva on Sunday.

'In the coming days, consultations with our partners will take place on the steps needed to end the war,' the Ukrainian leader wrote on X.

'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 – just as it has repeatedly committed crimes against our people and against other nations in the past.'

Zelensky has appointed his top aide, Andriy Yermak, to lead the talks, according to a presidential decree.

The decree said the talks will also include 'representatives of the Russian Federation.' There was no immediate confirmation from Russia whether it would join the talks.

US officials have told Nato allies they expect to push president Zelensky into agreeing the deal under the threat that if Kyiv does not sign, it will face a much worse deal in future.

Briefing ambassadors from Nato nations, US Army Secretary Dan Driscoll said: 'No deal is perfect, but it must be done sooner rather than later.'

Donald Trump has told his Ukrainian counterpart Volodymyr Zelensky that he has until Thursday to make up his mind, although there are signs there may be room for manoeuvre.

Vice President JD Vance has insisted the US administration's approach is rooted in pragmatic diplomacy rather than unrealistic expectations.

He said: 'Every criticism of the peace framework the administration is working on either misunderstands the framework or misstates some critical reality on the ground.

'There is a fantasy that if we just give more money, more weapons, or more sanctions, victory is at hand.'

Mr Zelensky said he would work around the clock to find a path but insisted he would not betray his country.

If he accepts the deal, Ukraine would have to cede to Russia all the lands that Moscow has declared for itself in Donetsk and Luhansk. These would then be recognised by the US as Russian territory.

No NATO forces could be based inside Ukraine. And the Ukrainian military would be cut by a quarter to 600,000 troops and barred from possessing long-range weapons that could reach Russia.

Starmer held 25-minute talks with France's Emmanuel Macron and Germany's Friedrich Merz, before the meeting was expanded to include a dozen G7 and G20 leaders including from Japan, Canada, Italy, Norway and the European Union.

A joint statement issued following their meeting at the Johannesburg G20 summit said: 'We welcome the continued US efforts to bring peace to Ukraine.

'The initial draft of the 28-point plan includes important elements that will be essential for a just and lasting peace.

'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.

'We reiterate that the implementation of elements relating to the European Union and relating to Nato would need the consent of EU and Nato members respectively.

'We take this opportunity to underline the strength of our continued support to Ukraine. We will continue to coordinate closely with Ukraine and the US over the coming days.'

Ahead of the talks, Sir Keir said: 'Ukraine's friends and partners will meet in the margins of the G20 summit to discuss how we can secure a full ceasefire and create the space for meaningful peace negotiations.

'We will discuss the current proposal on the table, and in support of President Trump's push for peace, look at how we can strengthen this plan for the next phase of negotiations.'

He added that there 'is only one country around the G20 table that is not calling for a ceasefire' as he condemned Moscow for sending nearly 1,000 drones and 54 precision guided missiles in the past week alone.

'Ukraine has been ready to negotiate for months, while Russia has stalled and continued its murderous rampage.

'That is why we must all work together, with both the US and Ukraine, to secure a just and lasting peace once and for all.

'We will continue to co-ordinate closely with Washington and Kyiv to achieve that.'

Sir Keir is understood to have ruled out flying to Washington next week though European leaders including France's Emmanuel Macron, Germany's Friedrich Merz and Italy's Giorgia Meloni are considering visiting Mr Trump.

Mr Putin, who like Mr Trump is not attending the gathering of the world's leading economies, has cautiously welcomed the US proposal, saying it 'could form the basis of a final peace settlement'.

With Ukraine facing one of the most 'difficult moments' in its history, Mr Zelensky said it faced a choice between 'losing its dignity or the risk of losing a key partner'

It followed his 40-minute call with Sir Keir, Mr Macron and Mr Merz, in which the European leaders emphasised that Ukraine 'must determine its future under its sovereignty'.

The Prime Minister said they had emphasised to Mr Zelensky their support for Ukraine and the 'fundamental principle' that Kyiv should be in charge of its own destiny.Asked what it meant to 'strengthen' Washington's plans, Downing Street declined to 'get ahead of those discussions' but denied they were viewed as weak by friends of Kyiv.

Pressed on whether Britain had been cut out of Mr Trump's peace negotiations, Sir Keir's spokesman said he did not 'accept that at all' as he stressed the 'excellent relationship' between the US and UK leaders.

EU foreign policy chief Kaja Kallas said in Brussels: 'Russia's war against Ukraine is an existential threat to Europe. We all want this war to end. But how it ends matters. Russia has no legal right whatsoever to any concessions from the country it invaded. Ultimately, the terms of any agreement are for Ukraine to decide.'

Meanwhile the Polish prime minister has insisted that a peace settlement cannot be imposed on Ukraine.

Karol Nawrocki said: 'It was Ukraine that fell victim to Putin's criminal aggression, and it is Ukrainians, with the support of the United States and EU countries, who must have the decisive voice in peace talks.

'The price of peace cannot in any way be the achievement of strategic goals by the aggressor, and the aggressor was and remains the Russian Federation.'

Significantly, Reform UK leader Nigel Farage was among those publicly criticising the deal. He warned Trump, a friend and ally, that asking Ukraine to slash its military was 'not acceptable'