Jaap de Hoop Scheffer, Nato's secretary-general, has warned Vladimir Putin that next week's summit of the 26-member Atlantic alliance must not be marred by a new display of "unhelpful rhetoric" from Russia's president, directed at the west.

As the military alliance's national leaders prepare to meet in Bucharest for the annual gathering, tensions between Nato and Russia are running high because of Washington's insistence that Ukraine and Georgia should be allowed to take a significant new step towards joining the organisation.