British infantry will take part in a training mission in Ukraine, David Cameron has announced.
The military personnel will help train the Ukrainian army and supply tactical intelligence, the Prime Minister told MPs on the Liaison Committee.
Sky’s Defence Correspondent Alistair Bunkall reports that around 75 British soldiers will go from the beginning of March and will be based in the west of the country, some of them for up to six months.
He said: “We are talking about medical training, infantry training, intelligence logistics and the like.
“So this is not arming them with weapons, it is arming them with knowledge and it is another aspect to Britain’s help for the Ukrainian government to help them repel the Russian rebels.
Mr Cameron told MPs Britain would be “the strongest pole in the tent” making the case for harsher sanctions against Russia if pro-Moscow separatists in eastern Ukraine fail to observe the ceasefire.
Russian President Vladimir Putin denies arming the rebels in a war that has killed more than 5,600 people and forced over a million to flee their homes.
There would be “deeply damaging” consequences for Europe if the EU fails to stand up to Mr Putin over the crisis, the PM warned.
He added the Russian leader could target the Baltic states or Moldova if he is not reined in.
Mr Cameron told MPs he did not rule out arming Ukraine at some point in the future, but said supplying non-lethal support was the current approach.
It comes as European foreign ministers called for those involved in the fighting in the east of Ukraine to abide by the ceasefire.
Mr Cameron said it would be “miraculous” if the terms of the agreement were met in full.
The EU’s foreign policy chief, Federica Mogherini, has told Sky News Tonight the ceasefire negotiated in Belarus is the only option to achieve peace.
Fighting has continued around the strategically important town of Debaltseve since the ceasefire was negotiated, and Mr Cameron said he feared the rebels would target the port of Mariupol next.
This fear was echoed by Ukrainian foreign minister Pavlo Klimkin, who was speaking after the Paris talks.
US Secretary of State John Kerry has meanwhile accused Russia of repeatedly lying to him over Ukraine.
Mr Kerry told a Senate subcommittee: “Russia is engaged in a rather remarkable period of the most overt and extensive propaganda exercise that I’ve seen since the very height of the Cold War.”
Separatists brought reporters to witness the withdrawal of heavy weapons from the front line under the ceasefire on Tuesday.
Kiev accuses the rebels of using the cover of the truce to reinforce for another advance.