Britain called on embattled Libyan leader Muammar Gaddafi to step down after his troops shelled parts of central Tripoli on Monday.
Prime Minister David Cameron has cut short a summer break in southwest England and returned to London where he will chair a security council meeting on Monday.
The end of Gaddafi's four-decade rule would be a welcome boost for Cameron's diplomatic policies after a difficult few months at home in which he has seen his image tarnished by the fall-out from a tabloid phone-hacking scandal and riots across major English cities.