Secretary of State Hillary Rodham Clinton implored the world on Tuesday to speak with a single voice and tell Muammar Qadhafi to leave power, as the Obama administration looked to expand ties with Libyan rebel leaders seeking an end to four decades of dictatorship.

Ms. Clinton told an international conference on Libya’s future that countries must work together so that the North African country “belongs not to a dictator, but to its people,” promising to ratchet up the pressure on the Libyan government in the hope of convincing Col. Qadhafi’s remaining loyalists to abandon the regime.

Addressing officials from more than three dozen countries, Ms. Clinton told the gathering in London that military means alone won’t force Col. Qadhafi out after 42 years in power, and that further sanctions and diplomatic pressure ought to be applied. Her comments come at a key turning point in the international military action in Libya, as the United States steps back from its lead role and transfers authority for the whole mission to NATO.

“All of us must continue to increase the pressure on and deepen the isolation of the Qadhafi regime through other means as well,” she said. “All of us seated around this table must speak with one voice in support of a transition that leads to a brighter future for Libya.”

Ms. Clinton spoke after meeting on the sidelines with Mahmoud Jibril, a representative of the Libyan opposition fighting Qadhafi, “to talk about the path forward.”

Meanwhile, a senior administration official said the U.S. will soon send an envoy to Libya to deepen relations with leaders of the rebels seeking to overthrow Col. Qadhafi.

Chris Stevens, who was until recently the deputy chief of mission at the now—shuttered U.S. Embassy in Tripoli, will make the trip in the coming days. The move doesn’t constitute formal recognition of the opposition, stressed the official, who spoke on condition of anonymity to discuss internal planning.

The London gathering comes a day after President Barack Obama vigorously defended the U.S.—led campaign against Col. Qadhafi’s troops in Libya, declaring that action was necessary to prevent a slaughter of civilians. A massacre would have stained the world’s conscience and “been a betrayal of who we are” as Americans, Mr. Obama said.

Yet the president ruled out targeting Col. Qadhafi, warning that trying to oust him militarily would be a mistake as costly as the war in Iraq, and said he would keep his pledge to get the U.S. out of the military lead fast.

Susan Rice, the U.S. ambassador to the United Nations, said on Tuesday “there are non—military means at our disposal” to force Col. Qadhafi out, including economic and diplomatic pressure.

She said on CBS’s “The Early Show” that the overriding aim of the American military intervention in Libya was to protect civilians and establish a no—fly zone. Ms. Rice acknowledged that Col. Qadhafi’s ouster “may not happen overnight.”

Appearing on the same show, Arizona Sen. John McCain said “I don’t think it’s possible” in the short—term to get Col. Qadhafi out without employing military force.

“Qadhafi in power is unacceptable,” he said. “We should use any means to bring him down.”

In the British capital, world powers will address some of the questions that have been raised since the international strikes against Col. Qadhafi began, from possible endgame scenarios for the regime to plans for the country’s post—dictatorship future.

The senior administration official said three practical outcomes were expected- recognition beyond NATO of the alliance’s new leadership in protecting Libyan civilians; the creation of a “contact group” to lead enforcement of U.N. sanctions and other political efforts against the Qadhafi regime; and a second trip to the country by U.N. special envoy Abdelilah al—Khatib, a former Jordanian foreign minister.

The official suggested that Mr. al—Khatib’s mission would be to negotiate the international community’s terms for a graceful exit for Col. Qadhafi to spare further bloodshed in Libya. But the official rejected the idea that the Libyan leader of 42 years could escape accountability and a possible war crimes trial as part of an agreement for him to go into exile, an idea floated by some in the coalition.

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