British military personnel are to be sent to Ukraine in the next few weeks to provide advice and training, says Prime Minister David Cameron.
As he spoke, pro-Russian rebels said they were pulling back heavy weapons from the front line in eastern Ukraine as part of a ceasefire.
However, the government in Kiev has disputed the rebel claims.
Mr Cameron said he would push for more sanctions on Russia if the separatists failed to observe the truce.
The prime minister told a House of Commons committee that up to 75 British soldiers divided into four teams would go to an area well away from the conflict zone to provide medical, logistics, intelligence and infantry skills.