Sir Keir Starmer has announced he is "ready and willing" to put British troops on the ground in Ukraine to enforce a peace deal.
The announcement comes ahead of a meeting with European leaders in Paris today, which was called by the French president, Emmanuel Macron, after it emerged EU leaders were not invited to early Ukraine peace talks between the US and Russia.
A senior member of Donald Trump's administration also signalled that US security support for Europe would be scaled back.
In an exclusive article for The Telegraph, the prime minister said he had not taken the decision to consider putting British servicemen and women “in harm’s way” lightly.
He also said the UK "are facing a once-in-a-generation moment" and suggested the UK could play a "unique role" as a bridge between Europe and the US in the peace process.
The prime minister will join the leaders of France, Germany, Italy, Poland, Spain, the Netherlands, Denmark, the European Commission, the European Council and Nato in Paris today, while foreign ministers of Russia and the US will meet in Saudi Arabia to kick off talks over a peace agreement.