The Obama administration pressed Thursday for greater United Nations authority to confront Libyan leader Moammar Gaddafi’s forces by land, air and sea, while insisting that Arab governments play a central role in any possible military action.

After a day of negotiations Wednesday in the U.N. Security Council, it remained unclear whether the United States or allied governments were making concrete plans to intervene militarily against Gaddafi’s forces, which have made significant gains on the ground against rebel strongholds.

But U.S. diplomats sent the clearest signal yet that the Obama administration is willing to contemplate military operations even beyond a no-fly zone to resolve the crisis in the oil-rich nation.

In Congress, lawmakers were split on whether the United States should support a U.N. Security Council resolution authorizing military intervention in Libya. Sen. John F. Kerry (D-Mass.), chairman of the Senate Foreign Relations Committee, called on the council Thursday to pass such a resolution immediately. But in a Thursday morning hearing on the issue, Sen. Richard G. Lugar (R-Ind.), the senior Republican on the committee, said the administration “should first seek a congressional debate on a declaration of war” against Libya before agreeing to any military intervention.

In the administration’s most direct endorsement of a new resolution, William J. Burns, undersecretary of state for policy, told the committee that “we are pressing for a new U.N. Security Council resolution to authorize a range of further actions against the Gaddafi regime.”

France announced Thursday morning that its foreign minister, Alain Juppe, was headed to New York “to ensure that this resolution be adopted as swiftly as possible.”

A senior French Foreign Ministry official said the resolution would establish a no-fly zone, authorize “all means” to protect civilians, strengthen sanctions against Gaddafi and his family and call for an immediate cease-fire between Libyan government and rebel forces.

The no-fly zone would not bar air traffic from all Libyan airspace but could be enforced over a narrow coastal zone, the official said, in effect protecting the rebels from airstrikes against Benghazi, the rebel capital, and the coastal highway. He also suggested that no-fly zone enforcement could include “a whole range” of military actions short of ground troops. Juppe said earlier this week that Gaddafi’s air force could be stopped if the several dozen planes at his disposal and their runways were taken out.

The provision on protecting civilians indicated that Gaddafi’s forces would be prevented from carrying out bloody reprisals in Benghazi or elsewhere along the coast.

The French official said France and Britain, with cooperation from one or two unspecified Arab countries, would be ready to start carrying out such a resolution within hours of its approval.

At Thursday’s Senate Foreign Relations Committee hearing, Kerry said the world “cannot simply watch from the sidelines as the Libyan people’s quest for democratic reform is met with violence.” He hailed the Arab League’s call for a U.N. no-fly zone as “an unprecedented signal that the old rules of impunity for autocratic leaders no longer stand,” but he warned that Gaddafi’s opponents are running out of time.

“The United Nations Security Council should act now — today — to pass a resolution that the United States has shown real leadership in crafting that would provide the range of options necessary to avert a humanitarian disaster,” Kerry said. In any case, Gaddafi “has no legitimacy to govern, and the will of the Libyan people will ultimately prevail,” he said.

Lugar questioned what he described as Obama’s lack of consultation and clarity of intent, recalling the Bush administration’s decision to go to war with Iraq without direct congressional authorization and raising the possibility of U.S. involvement in “a stream of civil wars” across the Middle East.

Lugar asked whether it was the administration’s view that it could commit U.S. forces to Libya without a declaration of war, “simply citing humanitarian considerations that people will be shot by oppressive rulers?” Burns did not reply directly, saying that he understood the “seriousness of your concerns” and would convey them to the White House and to Clinton.

Under further questioning, Burns agreed that the establishment of a no-fly zone would have little impact on conditions on the ground. He said the administration was “talking about a whole range of measures, including steps beyond a no-fly zone.”

Burns said the administration was “urgently” examining the Libyan opposition’s commitment to a democratic, secular government and has authorized the opposition’s governing body, the Transitional National Council, to open an office in Washington.

At the United Nations, U.S. Ambassador Susan E. Rice told reporters Wednesday, “We are discussing very seriously, and leading efforts in the council, around a range of actions that we believe could be effective in protecting civilians.” However, she added, “The U.S. view is that we need to be prepared to contemplate steps that include, but perhaps go beyond, a no-fly zone at this point, as the situation on the ground has evolved and as a no-fly zone has inherent limitations in terms of protection of civilians at immediate risk.”

Rice’s comment came as the Obama administration and other military powers confronted the realization that the window to push Gaddafi from power is closing as his forces bear down on Benghazi.

The lack of clarity over whether the United States and European nations would intervene raised the prospect that an emboldened Gaddafi, who Obama has said must leave office, will soon regain complete control of the nation and punish those who opposed him during weeks of fighting.

The resolution introduced Wednesday by Lebanon, Britain and France sparked negotiations on a range of military options — and what countries would carry them out — that U.S. diplomats acknowledge must be resolved quickly.

Even if adopted within days, a Libyan no-fly zone or a more aggressive no-drive and no-sail zone targeting Gaddafi’s armored and naval forces might not be enough to prevent the rebels’ defeat, some diplomats and analysts say.

“We are moving as rapidly as we can in New York to see whether we can get additional authorization for the international community to look at a broad range of actions — not just a no-fly zone, but other actions as well,” Secretary of State Hillary Rodham Clinton told reporters during a visit to Cairo.

Clinton, who toured Tahrir Square, the center of Egypt’s recent revolution, said she hoped that a vote on the resolution would come “no later than” Thursday and that the Arab League endorsement of a no-fly zone over the weekend would persuade such countries as Russia and China to support the measure.

In an interview with the BBC, Clinton said, “We are well aware that the clock is ticking.”

At the United Nations, Rice’s comments indicated that the United States might push for military operations and broader international participation than initially anticipated. She said the Security Council would continue debate and push for a vote on Thursday, “fully focused on the urgency and the gravity of the situation on the ground.”

Rice’s proposal suggests a shift in the administration’s initially cautious view of military action in Libya, driven in part by skepticism that a no-fly zone could prove decisive in helping the Libyan rebels.

Richard Haass, president of the Council on Foreign Relations, said in an interview earlier Wednesday on MSNBC that “this administration, correctly in my view, has never been all that enthusiastic about having a no-fly zone.”

“I think they correctively diagnosed it as not enough to be militarily decisive but enough to perhaps get you in trouble in Libya,” Haass said. “So that’s why they ruled out anything unilateral.” 

Obama has been content to let European allies lead the search for a resolution to the Libyan conflict, fearing that an overt U.S. endorsement of a no-fly zone or other measures would undermine the popular nature of the revolt in a country where the United States is deeply unpopular.

He has been equally cautious as uprisings have swept away autocratic governments in Tunisia and Egypt, and as demonstrators in Yemen, Bahrain, Jordan and other nations continue to demand more open government from the royal families and autocrats that have run them for decades.

But time is running short in Libya, where a rebel force that once held nearly half the country is being pushed back toward its stronghold in the eastern city of Benghazi.

“This is urgent,” Juppe declared on his blog Wednesday, adding: “We have often seen in our contemporary history that the weakness of democracies leaves the field open to dictatorships. It is not too late to defy this rule.”

France and Britain have taken the lead in drafting a no-fly resolution, and France’s chief Foreign Ministry spokesman, Bernard Valero, said the revised text now before the Security Council is probably the last real chance for the international community to act decisively in Libya.

“It is now up to everyone to assume his responsibilities,” he said.

Almost any kind of military intervention would be possible only with extensive cooperation from the United States, the only country able to field sufficient aircraft carriers, intelligence, command and control equipment, and warplanes on short notice.

Some conservatives worry that Obama will decline to act against Gaddafi, allowing the dictator to regain his 41-year hold over the country.

Elliott Abrams, a National Security Council staff director during the George W. Bush administration who has advised Obama on Egypt, asked “how, after saying he must go, you adopt a policy of inaction?”

“It’s as if this administration thinks American foreign policy consists of words, and it doesn’t,” Abrams said. “Does Gaddafi attempt to reassemble a nuclear weapons program? Does Gaddafi return to terrorism? Does Gaddafi massacre the people of Benghazi? All of these are possibilities, and any one of them would make President Obama's decision not to act look even worse than it does now.”

Lynch reported from the United Nations. Staff writer William Branigin in Washington, correspondent Edward Cody in Paris and staff writer Joby Warrick in Cairo contributed to this report.