Vladimir Putin is to attend a Nato summit in Bucharest in April, the first time the -Russian president has accepted an invitation from the defence alliance since 2002, when ties with the west were more cordial.

The announcement comes as Moscow and Nato head for a collision over the -alliance's plans to deploy a missile defence shield near Russia and the Kremlin's unilateral withdrawal from the Conventional Forces in Europe pact, a key post-Soviet arms treaty.