Cabinet planning action on Libya
David Cameron is chairing an emergency session of the Cabinet as British forces prepare to join international military action to protect Libyan civilians from Colonel Muammar Gaddafi's "brutal" crackdown.
The United Nations Security Council voted on Thursday night in favour of a wide-ranging resolution authorising the international community to take "all measures necessary" short of putting troops on the ground.
France, which has led calls with Britain for a no-fly zone, confirmed that its forces would participate, while Mr Cameron is expected to give details of what role the UK will play in a Commons statement at 11am.
US President Barack Obama telephoned Mr Cameron and French president Nicolas Sarkozy on Thursday to discuss the way forward. A White House statement said they agreed "to co-ordinate closely on next steps, and to continue working with Arab and other international partners to ensure the enforcement of UN Security Council resolutions on Libya".
Downing Street played down suggestions - raised by France in the run-up to the vote - that action could start within hours and US officials suggested it may take until Sunday to be ready. The news of the Security Council resolution was greeted with scenes of wild celebration in the rebel stronghold of Benghazi - thought to be the next target of the regime's counter-offensive.
But Gaddafi's son Saif reacted with defiance, telling America's ABC News: "Our country and our people are not afraid. The resolution is unfair, because as you know from the beginning we have proved to everybody that there have been no air strikes against civilians."
Among the first ministers to arrive in Downing Street for the Cabinet was Defence Secretary Liam Fox, accompanied by Chief of the Defence Staff General Sir David Richards.
Gaddafi has vowed to show "no mercy" to those involved in the uprising and showed no sign of accepting the immediate ceasefire demands included in the UN resolution.
The dramatic late-night vote at the Security Council in New York - by 10 to zero with five abstentions - came after days of stalling and intense telephone diplomacy by Mr Cameron with Arab, African and European leaders.
Foreign Secretary William Hague hailed the resolution as an essential step towards halting further bloodshed and said Britain "will now respond" to its responsibilities. The approval of the resolution meant all of the UK's criteria for a no-fly zone - a demonstrable need, a clear legal basis and broad regional support - were now met, he said.