Two influential US senators Monday filed a resolution calling for President Barack Obama to recognize the Libyan opposition force battling against the regime of Moamer Kadhafi.

The resolution, which does not carry the weight of becoming law if passed, also urges Obama to support a proposed no-fly zone over Libya to protect the rebels, who have been in retreat from Kadhafi's forces in recent days.

It also asks Obama's administration to develop a strategy aimed at fulfilling the president's stated goal: the end of the Kadhafi regime.

Senator John McCain, who co-authored the resolution with Senator Joseph Lieberman, told journalists that the United States should recognize the Libyan rebel council as a legitimate government "like the French did," he said.

France was the first country -- and Monday remained the only one -- to recognize the Transitional National Council as a legitimate representative of Libya.

McCain, the Republican candidate for president in 2008, discounted as "foolish" the argument by some in Washington that the United States should not yet recognize the opposition group because not enough is known about them.

Obama on Monday issued a new warning to Kadhafi: "Mr Kadhafi has lost his legitimacy and he needs to leave."

US Secretary of State Hillary Clinton was meeting Monday in Paris with representatives of the Libyan opposition group but Washington was not expected yet to make a formal recognition.

McCain, in a speech on the Senate floor, called on Obama to back up his words with action.

"Libya is the real test. It is the test of whether we will provide our support not just when it is easy but when it is difficult -- when it requires more of us than just speeches and expressions of solidarity."

The United States should also consider assistance to the rebels including sharing intelligence "and even forms of security assistance if they request it, and if we can provide it in a responsible way," McCain said.

McCain cited former US president Bill Clinton's recent remarks that "it's not a fair fight" between the rebels and Kadhafi's better-armed forces.

"Mr President, our window of opportunity to support the Libyan people is closing quickly," he said.

The lightly-armed rebels have been pushed back some 124 miles (200 kilometers) by superior forces in the past week and are now only 105 miles (170 kilometers) from Benghazi, their stronghold.

Rights groups say thousands of people have been killed in Libya since Kadhafi started a crackdown against protesters and his forces launched an offensive against rebel-held areas.

The UN Security Council has passed sanctions against the Libyan regime and the Arab League has joined Britain and France in calling for the council to order a no-fly zone over Libya.

There was no immediate vote on the resolution.