Diplomats said it appeared unlikely there would be another vote to try to renew the mandate before it expires on April 30
It added that the attack was made in response to Islamic State calls to target countries that have been part of a coalition fighting the jihadist group.
British police on Friday shot dead a man wearing a fake suicide vest who stabbed two people to death in London and wounded three more before being wrestled to the ground by bystanders, in what the authorities called a terrorist attack.