LONDON (REUTERS) - Prime Minister David Cameron said on Tuesday Britain would deploy military personnel to Ukraine in the next month to help train the Ukrainian army, warning that Moscow would move to destabilise other countries if left unchallenged.

Cameron made the announcement after pro-Russia separatists brought reporters to witness the withdrawal of heavy weapons from the front line in eastern Ukraine under a ceasefire deal.

Ukraine said the rebels were using the cover of the truce to reinforce for another advance.

"Over the course of the next month we're going to be deploying British service personnel to provide advice and a range of training, to tactical intelligence to logistics, to medical care," Cameron told a committee of lawmakers in parliament.

"We'll also be developing an infantry training programme with Ukraine to improve the durability of their forces," he added, stressing British personnel would be a long way from any front line and not be involved in combat operations.

Cameron said he did not rule out arming Ukraine at some point in the future but that supplying non-lethal support was Britain's current approach.

"If we don't stand up to Russia in the long-term it will be deeply damaging to all of us because you'll see further destabilisation. Next it'll be Moldova or one of the Baltic states."