The United States is moving naval and air forces, including an aircraft carrier, into the Mediterranean Sea near Libya, U.S. officials said Monday, as the Obama administration and its allies consider how to respond to Libyan leader Moammar Gadhafi’s brutal efforts to suppress a widespread rebellion among civilians and army troops.

The U.S. decision comes as Gadhafi appeared to be making a concerted effort to retake control of Zawiya, a town about 30 miles west of Tripoli that has been in rebel hands since last week. Two people reached separately by phone said heavy fighting had broken out in the early evening Monday as militias loyal to Gadhafi attacked from both the east and the west.

U.S. officials said no decision had been made on how the U.S. forces would be used, but that one option under consideration is the imposition of a no-fly zone designed to prevent Gadhafi from using aircraft as he fought the rebels.

“”We have planners working and various contingency plans, and I think it’s safe to say as part of that we’re repositioning forces to be able to provide for that flexibility once decisions are made,”” Marine Col. David Lapan, a Pentagon spokesman, told reporters.

Another official, who requested anonymity to discuss the issue, said the pre-positioning of military assets “”doesn’t mean to suggest that there will be military intervention.””

At the same time, he said, consideration of imposing a no-fly zone “”has picked up a little speed.””

Gadhafi opponents in Libya’s second-largest city, Benghazi, have said they oppose foreign military intervention, a message they reiterated in comments on Twitter after thePentagon moves became public.

A no-fly zone would seek to prevent Gadhafi from using aircraft to attack protesters, move equipment and personnel, or ferry in foreign mercenaries who have been killing Gadhafi’s opponents.

The White House, which has called on Gadhafi to leave power, said Monday that “”exile is certainly one option”” for the Libyan dictator.

It was not immediately clear which countries would be willing to take Gadhafi in or whether the United States had made efforts to arrange asylum. Gadhafi and his family have publicly declared they would not leave Libya.

White House press secretary Jay Carney said implementing a no-fly zone over Libyan airspace is “”an option we are actively considering.””

Carney spoke as Secretary of State Hillary Clinton conferred with colleagues in Geneva, Switzerland. President Barack Obama and U.N. Ambassador Susan Rice were to meet Monday afternoon in Washington with U.N. Secretary-General Ban Ki-moon.

The administration officials could not say which U.S. aircraft carrier will be dispatched as part of the international response, as there currently are none in the Mediterranean.

Carney declined to describe the level of contact been the U.S. government and Libyan opposition forces. He said it is “”premature to make decisions about recognizing one group or the other,”” but that the administration has “”a variety”” of channels through which to communicate with opposition forces.

In Geneva, Clinton joined foreign ministers from around the world in an extraordinary session of the U.N. Human Rights Council to discuss the upheaval in Libya.

In her address, Clinton repeated a U.S. call for Gadhafi to step down.

“”We have seen Colonel Gaddafi’s security forces open fire on peaceful protesters. They have used heavy weapons on unarmed civilians. Mercenaries and thugs have been turned loose to attack demonstrators,”” Clinton said. “”Through their actions, they have lost the legitimacy to govern. And the people of Libya have made themselves clear: It is time for Gaddafi to go. Now. Without further violence or delay.””

News reports Monday said Gadhafi had appointed his intelligence chief, Bouzaid Dordah, to negotiate with the temporary government that is being formed in eastern areas freed from his control.

But in Benghazi, officials flatly closed the door to negotiations. The bloodshed across the country, including roughly 300 killed in Libya’s second-largest city, makes that impossible, local officials said.

“”There is only (one) demand; Gadhafi has to leave,”” said Abdullah Shamia, an adviser to the 13-member committee in charge of Benghazi. “”There is no negotiation.””