WASHINGTON (AP) — The Obama administration on Friday insisted that Libya's Moammar Gadhafi gave the world no choice but to threaten military action against him, but it left unclear what role U.S. forces might play in providing air cover for rebels or launching strikes to force Gadhafi from power.

Secretary of State Hillary Rodham Clinton told reporters that Gadhafi must make "a very clear set of decisions" to halt violence against anti-government rebels. But her comments also seemed to tamp down expectations of imminent U.S. military action, as Pentagon officials mulled options.

Clinton said the U.S. had seen the reports of a cease-fire by the Libyan government, but added that "we are going to be not responsive or impressed by words." She said the immediate objective of any intervention was to halt the violence against civilians, but insisted that the "final result of any negotiation would have to be the decision by Col. Gadhafi to leave."

The U.S. has ships and warplanes within striking distance of Libya, including submarines and surface ships armed with Tomahawk cruise missiles. If military action were to proceed, a first step likely would involve attacks on Libyan air defenses, including radar and surface-to-air missile sites along its Mediterranean coastline. That would allow aircraft enforcing a no-fly zone to maneuver with impunity.

The nearest U.S. aircraft carrier, the USS Enterprise, was far to the east, in the Arabian Sea supporting air operations in Afghanistan. The Pentagon gave no indication that substantial additional firepower was being moved toward Libya, even as it focused on providing humanitarian relief in stricken northern Japan.

The White House said President Barack Obama would confer Friday with congressional leaders of both parties on the Libya situation and then make a public statement. Defense Secretary Robert Gates, who has been publicly skeptical of U.S. military involvement in Libya, was out of sight, preparing for an overseas trip starting Saturday.

Clinton applauded a U.N. Security Council resolution authorizing a no-fly zone and "all necessary measures" to prevent Gadhafi from continuing attacks on his own people, but she did not spell out the next step.

"While this resolution is an important step, it is only that — an important step," she said. "We and our partners will continue to explore the most effective measures to end this crisis."

Britain, France and NATO were holding emergency meetings Friday on using military force to enforce a no-fly zone. NATO Secretary-General Anders Fogh Rasmussen said the alliance was "completing its planning to be ready to take appropriate action in support of the U.N. resolution as part of the broad international effort."

Officials announced that the leaders of Britain, France and Germany and the chiefs of the United Nations and Arab League would join other world leaders for an emergency summit on Libya in Paris on Saturday.

Clinton said the first goal of international action is to end the violence in Libya and that the regime's forces need to pull back "a significant distance away from the east, where they have been pursuing their campaign against the opposition."

The larger objective remains Gadhafi's ouster.

Clinton's comments came after the administration and America's allies won an open-ended endorsement Thursday from the United Nations for military action in Libya, where Gadhafi's regime has led a bloody campaign to suppress dissent and eliminate any opposition to his 42-year rule.

The breakthrough at the U.N. Security Council came after days of cautious diplomacy from the administration and set the stage for airstrikes, a no-fly zone and other military measures short of a ground invasion to halt the violence in Libya and push Gadhafi from power.

Defense analysts caution that information about Libya's military capabilities is murky, particularly since some troops have defected, taking aircraft or other weaponry with them. Analysts said Friday that Libya has about 180 aircraft, including fighters, some bombers and some transport planes. But many of those are believed to be of limited value in combat.

Britain said Friday it will send Typhoon and Tornado fighter jets to air bases "in the coming hours" to prevent Gadhafi's forces from mounting air strikes against the rebels. France has also spoken on swift action, while Italy announced that it will allow its military bases to be used for the U.N.-backed military intervention.

The U.S. hasn't revealed what role it will play, but it has a vast array of naval and air forces in the region, some positioned there in recent weeks for a possible response to the fighting and resulting humanitarian crisis.

Among ships the U.S. has in the Mediterranean area are the nuclear-powered submarine USS Providence, equipped with Tomahawk missiles; the amphibious landing dock USS Ponce and amphibious assault ship USS Kearsarge, with a contingent of 400 Marines and dozens of helicopters; the command ship USS Mount Whitney and destroyers USS Mason, USS Barry and USS Stout.

The U.S. backing for international action comes after several administration officials questioned the plan for providing aerial cover, with the Pentagon perhaps the most vocal in its skepticism. It has described the no-fly zone as a step tantamount to war, and a number of U.S. officials have expressed fears that involvement in Libya could further strain America's already stretched military and entangle the country in an expensive and messy conflict in another Muslim country.

Clinton said the U.N. Security Council's 10-0 vote authorizing military action "sent a strong message that needs to be heeded," and that Gadhafi's refusal to hear the repeated calls for him to stop the bloodshed had forced the world to pursue military action.

Gadhafi "cannot continue his violence against his own people," she said after a meeting with Ireland's foreign minister. "He cannot continue to attack those who started out peacefully demonstrating for changes."

Just Thursday, speaking in Tunisia, Clinton spoke cautiously about the possibility of a no-fly zone, saying it would require action to protect the planes and pilots, "including bombing targets like the Libyan defense systems." But pressed on by Britain and France, and buoyed over the weekend by the surprise support of the Arab League, the no-fly option gained traction.

After the resolution, Obama spoke Thursday with French President Nicolas Sarkozy and British Prime Minister David Cameron and the leaders "agreed that Libya must immediately comply with all terms of the resolution and that violence against the civilian population of Libya must cease," according to a White House statement.

Even before the Security Council vote, the Obama administration readied plans to enforce the no-fly zone, with congressional officials describing a closed-door briefing in which the administration said it could ground Gadhafi's air force by Sunday or Monday. The effort likely will involve jet fighters, bombers and surveillance aircraft, officials said, and the U.S. is keen to have Arab countries such as Jordan, Qatar and the United Arab Emirates participate in the operation.

For Obama, the shift to international action arrived as he faced increased criticism for not moving aggressively enough to help the rebels trying to topple Gadhafi, long counted as among the world's most ruthless rulers. Some U.S. lawmakers demanded the no-fly zone, while others have proposed more strident measures such as supplying the opposition with arms.