LONDON (Reuters) - Britain and the United States stepped up pressure on Libyan leader Muammar Gaddafi to quit on Tuesday, and rebels fighting him promised to build a free, democratic state if they won power in Tripoli.
British Prime Minister David Cameron, opening a conference of 40 governments and international bodies on Libya, accused Gaddafi's supporters of "murderous attacks" on people in Misrata, Libya's third largest city.
U.S. Secretary of State Hillary Clinton said that coalition military strikes on Libya would continue until Gaddafi fully complied withU.N. demands to cease violence against civilians and pull forces out of occupied cities.
"All of us must continue to increase the pressure on and deepen the isolation of the Gaddafi regime through other means as well," Clinton said.
"This includes a unified front of political and diplomatic pressure that makes clear to Gaddafi that he must go."
On Libya's coastal strip, focus of fighting, Gaddafi's better armed troops appeared to be reversing a recent westward charge by rebels who had taken advantage of coalition air strikes to seize a string of towns over the last week.
Gaddafi accused Western powers of massacres of Libyan civilians in alliance with rebels he said were al Qaeda members.
Before the London conference, called to discuss current action against the Tripoli government and a post-Gaddafi era, the interim rebel National Council held out the prospect of a "modern, free and united state" if Gaddafi could be ousted.
Mahmoud Jebril, a leader of the Benghazi-based National Council, was in London for meetings with Cameron and Clinton.
An eight-point Council statement said the oil-producing north African nation's economy would be used for the benefit of all Libyans. It also said it would draft a national constitution allowing the formation of political parties and trades unions.
Its commitments included guaranteeing "every Libyan citizen, of statutory age, the right to vote in free and fair parliamentary elections and presidential elections, as well as the right to run for office."
With Gaddafi loyalists pushing back against rebels, Italy has put forward a proposal for a political deal to end Libya's crisis, including a quick ceasefire, exile for Gaddafi and dialogue between rebels and tribal leaders.
British Foreign Secretary William Hague also implied exile might be a way to take Gaddafi out of the picture and settle the six-week-old uprising against his four-decade rule.
"We want him to leave power and that's what we've consistently said to the Libyan regime. We are not in control, of course, of where he might go," Hague told the BBC, adding he believed Gaddafi should face the International Criminal Court.
Britain and France led the push for a muscular intervention in the Libyan conflict and coalition air strikes have helped rebels in the east of the country to advance; but questions remain about the end game in Libya.
Tuesday's meeting, due to end with a news conference at 1630 GMT, is expected to set up a high-level steering group, including Arab states, to provide political guidance for the international response to Libya.
(Additional reporting by Adrian Croft, Tim Castle, Stefano Ambrogi, William Maclean,Simon Cameron-Moore, Andrew Quinn, David Brunnstrom; Tracy Rucinski in Madrid; Silvia Aloisi in Rome; Yann Le Guernigou, Emmanuel Jarry, Brian Love, John Irish inParis, Editing by Ralph Boulton)