UK Prime Minister Keir Starmer has announced a four-point plan to work with Ukraine to end the war and defend the country from Russia.

The UK, France and other countries will step up their efforts in a "coalition of the willing" and seek to involve the US in their support for Ukraine, he said.

"We are at a crossroads in history today," Starmer said after a summit of 18 leaders - mostly from Europe and including Ukrainian President Volodymyr Zelensky, who said Ukraine felt "strong support" and the summit showed "European unity at an extremely high level not seen for a long time".

It comes two days after a fiery exchange between the Ukrainian leader and US President Donald Trump in the White House.

"We are all working together in Europe in order to find a basis for cooperation with America for a true peace and guaranteed security," Zelensky said after the summit.

Speaking at a news conference shortly after the meeting of leaders, Starmer said four points had been agreed:

• to keep military aid flowing into Ukraine, and to keep increasing the economic pressure on Russia
• that any lasting peace must ensure Ukraine's sovereignty and security and Ukraine must be present at any peace talks
• in the event of a peace deal, to boost Ukraine's defensive capabilities to deter any future invasion
• to develop a "coalition of the willing" to defend a deal in Ukraine and to guarantee peace afterwards

Sir Keir also announced an additional £1.6bn ($2bn) of UK export finance to buy more than 5,000 air defence missiles. This comes on top of a £2.2bn loan to provide more military aid to Ukraine backed by profits from frozen Russian assets.

"We have to learn from the mistakes of the past, we cannot accept a weak deal which Russia can breach with ease, instead any deal must be backed by strength," he said.

The prime minister did not state which countries had agreed to join this coalition of the willing, but said that those who had committed would intensify planning with real urgency.

The UK, he said, would back its commitment with "boots on the ground, and planes in the air".

"Europe must do the heavy lifting," he said, before adding that the agreement would need US backing and had to include Russia, but that Moscow could not be allowed to dictate terms.

"Let me be clear, we agree with Trump on the urgent need for a durable peace. Now we need to deliver together," Sir Keir said.

When asked if the US under Trump was an unreliable ally, he said: "Nobody wanted to see what happened last Friday, but I do not accept that the US is an unreliable ally."

Countries at the summit included France, Poland, Sweden, Turkey, Norway, the Czech Republic, Denmark, Germany, the Netherlands, Romania, Finland, Italy, Spain and Canada.

European Commission President Ursula von der Leyen said there was an urgent need to "re-arm Europe".

These sentiments were echoed by Nato Secretary General Mark Rutte, who said the meeting had seen European countries "stepping up" to make sure Ukraine has what it needs to "stay in the fight as long as it has to continue".

After the summit, Zelensky went to Sandringham where he met King Charles III. He later spoke to reporters at a final press briefing where he said he was ready to sign a deal on minerals with the US.

Ukraine was expected to sign the deal - which would grant the US access to Ukraine's rare mineral reserves - during Zelensky's visit to Washington, but the Ukrainian delegation ultimately left early after a heated confrontation with Trump in the Oval Office.

Earlier on Sunday, US Treasury Secretary Scott Bessent warned a deal on minerals between the US and Ukraine could not be signed "without a peace deal" with Russia.

But when asked by the BBC about the future of the deal following the summit, Zelensky said it was ready to be signed.

"The agreement that's on the table will be signed if the parties are ready," he said.

Sunday's summit concludes a hectic week of diplomacy, which included visits to Washington by French President Emmanuel Macron, Sir Keir and Zelensky.

However, Zelensky's meeting culminated in a heated exchange with Trump and US Vice-President JD Vance, in which the US president accused his Ukrainian counterpart of "gambling with World War Three".

Trump has said he wants to end the war in Ukraine and has expressed trust in Russian President Vladimir Putin, to the consternation of many of his Western allies.

The US has also begun peace talks with Russia - excluding Ukraine.

At one point, the US leader accused Ukraine of starting the war - even though it was Putin who launched a full-scale invasion of Russia's neighbour on 24 February 2022.