Jaap de Hoop Scheffer, Nato’s secretary-general, has warned Vladimir Putin that next week’s annual summit of the 26-member alliance must not be marked by another display from the Russian president of “unhelpful rhetoric” directed at the west.

As the alliance members’ heads of government prepare to meet in Bucharest, tensions between Nato and Russia are running high because of Washington’s insistence that Ukraine and Georgia should be allowed to take a major new step towards joining the organisation.