The UK and France have signed a declaration of intent on deploying troops in Ukraine if a peace deal is made with Russia, UK Prime Minister Sir Keir Starmer has announced.
After talks with Ukraine's allies in Paris, he said the UK and France would establish military hubs across Ukraine to deter future invasion, while French President Emmanuel Macron later said thousands of troops may be deployed.
Allies also largely agreed robust security guarantees for Ukraine and proposed that the US would take the lead in monitoring a truce. But the key issue of territory is still being discussed.
Russia has repeatedly warned that any foreign troops in Ukraine would be a legitimate target.
Moscow has not yet commented on the announcements made in the French capital.
Russian President Vladimir Putin launched a full-scale invasion of Ukraine in February 2022, and Moscow currently controls about 20% of Ukrainian territory.
Heads of state and top officials from the Coalition of the Willing took part in Tuesday's talks in Paris.
Speaking at a joint press conference after the meeting, Starmer said: We signed a declaration of intent on the deployment of forces to Ukraine in the event of a peace deal. This is a vital part of our commitment to stand with Ukraine for the long-term.
It paves the way for the legal framework under which British, French, and partner forces could operate on Ukrainian soil, securing Ukraine's skies and seas, and regenerating Ukraine's armed forces for the future.
The UK prime minister added London would participate in any US-led verification of a potential ceasefire.
Top US negotiator Steve Witkoff said durable security guarantees and robust prosperity commitments are essential to a lasting peace in Ukraine - referring to a key demand made by Kyiv.
Witkoff said the allies largely finished their work on agreeing security protocols so that people of Ukraine know that when this [war] ends, it ends forever.
Meanwhile, President Macron said Ukraine's allies had made considerable progress at the talks.
Ukrainian President Volodymyr Zelensky said a huge step forward had been made in Paris, but added that he would only consider efforts to be enough if they resulted in the end of the war.
Ukraine's president clearly hopes that guarantees of American monitoring, a multinational force on Ukrainian soil and more weapons support for his armed forces, will convince a sometimes-sceptical population that he is right to sue for peace, bolstered by a growing international coalition.
But, in concluding the Paris press conference, Zelensky acknowledged Tuesday's milestone did not necessarily guarantee peace. Real progress still needs Russian support, and Moscow has been notably silent in recent days about diplomatic efforts to end the war.
Putin is known to oppose the prospect of a European-led international force in any disputed areas and will be reluctant to halt his troops', albeit slow, advance if Moscow's war objectives have not been realised.
But pressure is undoubtedly growing on both sides to make compromises and end the war.
Last week, Zelensky said a peace deal was 90% ready. Agreeing on the remaining 10% would determine the fate of peace, the fate of Ukraine and Europe.
Territory and security guarantees have been at the forefront of unresolved issues for negotiators.
Zelensky has so far ruled out ceding any territory, but has suggested that Ukraine could withdraw its troops to an agreed point - but only if Russia does the same.
Moscow currently controls about 75% of the Donetsk region, and some 99% of the neighbouring Luhansk. The two regions form the industrial region of Donbas.
The original US-led 28-point peace plan widely leaked to the media last year was seen by Kyiv and its European allies as being heavily skewed in Russia's favour.
This triggered weeks of intensive high-level diplomacy - with Ukraine, the US and European leaders trying to amend the draft.
Last month, Kyiv sent the US an updated 20-point plan - as well as separate documents outlining potential security guarantees and provisions for Ukraine's reconstruction, Zelensky said.
