US Secretary of State Hillary Clinton acknowledged today that there was an "urgency" about the Libyan crisis as forces loyal to Muammar Gaddafi advance rapidly on the rebel-held east.

"We want to do what we can to protect innocent Libyans against the marauders let loose by the Gaddafi regime," Clinton said in an interview with CBS television while on a visit to Libya's eastern neighbour Cairo.

"And yes, time is fast upon us. There is an urgency to it."

Clinton stopped short of explicitly backing a no-fly zone, saying only that it was one of a number of options under consideration to protect Libyan civilians.

But she said that a statement issued by the Arab League on Saturday endorsing action against one of its own member governments, up to and including a no-fly zone, had had a major impact on the views of the major powers on the UN Security Council.

"I think that there was a sea change in opinion when the Arab League issued its statement on Saturday," she said.

"For the Arab League to call for military action to protect civilians in Libya, against a member of the Arab League, was an extraordinary statement of leadership and real conviction.

"That has changed the thinking of a lot of people. In fact, as we consult in New York on the UN resolution, there is a much greater openness than there was a week ago.

"Many of the countries on the Security Council that were reluctant or opposed are now willing to discuss what might be possible because of that Arab League statement."

Asked specifically about opposition from veto-wielding permanent members China and Russia, Clinton said: "I think they are willing to talk about what's at stake here.

"The Arab League taking that position has, I think, opened up some doors that were closed," she added.