The top two U.S. defense officials have not confirmed if the Libyan government has been firing on its own people from aircraft.

A reporter asked Defense Secretary Robert Gates and Joint Chiefs of Staff Adm. Mike Mullen on Tuesday if they had independent confirmation or had evidence that there had been air attacks on Libyans. The answer was no.

We've seen the press reports, but have no confirmation of that, Gates said at press conference.

That's correct. We've seen no confirmation whatsoever, Mullen said.

The responses come as U.S. military ships head to the Mediterranean Sea to support a humanitarian aid mission to the deliver aid to Northern Africa. Libyan refugees are leaving to neighboring Egypt and Tunisia amid reports of armed conflict between Libyan government forces and protesters.

I have directed several Navy ships to the Mediterranean, Gates said. The USS Kearsarge and the [USS] Ponce will be entering the Mediterranean shortly and will provide us a capability for both emergency evacuations and also for humanitarian relief.

The Kearsarge is an 844 foot amphibious assault ship that can support a Marine landing force, including helicopters and Harrier jets. The Ponce is a 540 foot support ship for amphibious landings. Gates said there would be 400 Marines supporting the Kearsarge's mission.

Secretary of State Hillary of Clinton told lawmakers on Tuesday that combatant commands are positioning assets to prepare to support these critical civilian humanitarian missions.

Clinton the U.S. was considering all possible options for action.

[W]e are taking no options off the table so long as the Libyan Government continues to turn its guns on its own people, she said.

Sen. John McCain, R-AZ, called for a no-fly zone over the country on Sunday.

Libyan pilots aren't going to fly if there is a no-fly zone and we could get air assets there to ensure it, McCain said on Sunday. I'm not ready to use ground forces or further intervention than that.

U.K. Prime Minister David Cameron has also said the no-fly zone is being considered. Australian Foreign Minister Kevin Rudd has called for it. Rudd told AAP in Geneva that we cannot afford Gaddafi to have yet more resources to bring about mass violence on his own people.

Russian Foreign Minister Sergei Lavrov called the idea of putting in place the no-fly zone superfluous, according to the Financial Times. Turkish Prime Minister Recep Tayyip Erdogan told the news outlet doing so would be an absurdity.

Venezuelan President Hugo Chavez on Monday denounced the U.S. stance, saying it was irresponsible to consider all options to resolve the situation in Libya, including an invasion. He proposed establishing a goodwill commission to mediate between the government and opposition protesters.

I think they're crazy for Lybian oil, he said.

The United Nations Security Council - which includes China, France, Russian, and the United Kingdom - has authorized an arms embargo, Libyan assets freeze, and travel ban for some Libyan officials, as well as humanitarian aid.  The resolution did not mention military action.