Russian President Vladimir Putin would breach a peace deal with Ukraine if it is not defended, Sir Keir Starmer has said, after attending a meeting of senior military leaders in London, BBC reported.

The UK prime minister said any agreement to stop the fighting between Russia and Ukraine would "only be lasting" if there were "security arrangements in place".

He was speaking at Permanent Joint Headquarters in Northwood, London, where more than 20 countries gathered at a closed meeting to discuss proposals for troops in Ukraine to help guarantee the country's security as part of any peace deal.

Sir Keir said security arrangements would make clear to Russia there would be "severe consequences if they are to breach any deal".

The prime minister said the UK and its allies were moving from "political momentum" to "military planning", which he said had "to be done now" before a deal was agreed.

He said: "It is vitally important we do that work because we know one thing for certain, which is a deal without anything behind it is something that Putin will breach, according to BBC.

"We know that because it happened before. I'm absolutely clear in my mind it will happen again".

Sir Keir ruled out redeploying UK troops from countries such as Estonia to commit to Kyiv, saying: "There's no pulling back from our commitments to other countries."