* Gates: Libya not vital to U.S. interests, but region is
* Gaddafi regime may fracture, U.S. officials say
* McCain calls policy confused, wants Obama to clarify (Adds UN envoy, British Foreign Office, paragraph 18)
By Arshad Mohammed
WASHINGTON, March 27 (Reuters) - The United States will cut its military role in Libya in the next week or so and start to focus with other nations on how to ease Libya's Muammar Gaddafi from power, top U.S. officials said on Sunday.
In television interviews, the U.S. secretaries of state and defense raised the possibility that Gaddafi's government could splinter and said a London conference on Tuesday would discuss political strategies to end his 41-year rule of the oil-exporting North African nation.
Secretary of State Hillary Clinton said on NBC's "Meet the Press" the United Nations would be sending a special envoy to Tripoli in the next few days with "a very clear message" to Gaddafi.
The United States and others began bombing Libya on March 19 to impose a no-fly zone and to keep Gaddafi's forces from attacking rebels and civilians in the east of the country, the latest Arab nation to see uprisings against authoritarian regimes.
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Defense Secretary Robert Gates said Libya was not vital to U.S. interests but the broader Middle East was, arguing that instability in Libya could undermine democratic transitions under way in neighboring Egypt and Tunisia.
"I don't think it's a vital interest for the United States. But we clearly have interests there," he told NBC in an interview taped on Saturday and broadcast Sunday.
"It's part of the region, which is a vital interest for the United States," he added.
Libyan rebels have pushed west to recapture more territory abandoned by Gaddafi's retreating forces, which have been weakened by Western air strikes and, according to Gates, are largely unable to move tanks and other armored vehicles.
"His ability to move armor, to move toward Benghazi or a place like that, has pretty well been eliminated," Gates told ABC's "This Week" program in one of three joint interviews with Clinton taped on Saturday.
Gates said the United States will move to a supporting role of intelligence, surveillance and reconnaissance, and maybe some mid-air refueling, once NATO assumes responsibility for the whole Libya operation. He stressed that President Barack Obama had ruled out putting U.S. ground troops into Libya.
CRACKS IN GADDAFI SUPPORT
Both Clinton and Gates spoke of a political push to try to find a way to ease Gaddafi from power, saying that this effort was gathering steam and it was possible more of Gaddafi's associates, including in the military, would turn against him.
"We have a lot of evidence that people around him are reaching out" to the international community, Clinton told NBC.
She said the U.S. message to those around Gaddafi was: "Now is your time to get out of this and to help change the direction" or else become pariahs and face possible prosecution by the International Criminal Court.
"We have things in our tool box in addition to hammers ... one should not underestimate the possibility of the regime itself cracking," Gates told NBC.
"This, eventually, is going to have to be settled by the Libyans themselves -- perhaps the U.N. can mediate or whatever -- but in terms of the miliary commitment, the president has put some very strict limitations," he added.
Clinton told NBC that the London conference, which she will attend, would "begin to focus how we are going to help facilitate such a transition of him leaving power."
Obama has said the purpose of the military action was to protect civilians not to oust Gaddafi. However, he and other officials have made no secret of the desire to see Gaddafi go.
The U.N. envoy, former Jordanian foreign minister Abdelilah Al-Khatib, was likely to travel to Libya after attending the London conference, which the British Foreign office says will aim to "begin to support a new political future for Libya."
Senate Armed Services Committee Chairman Carl Levin, a Democrat like Obama, said on CNN's "State of the Union" program the goal is to prevent the slaughter of civilians in Libya and the mission was succeeding.
"It has set Gaddafi back. He is on his heels now," he said. Asked if the goal should be to remove Gaddafi, he said: "There are other means of removing Gaddafi than military means.
"We saw that in Egypt where the people of Egypt removed their dictator. The people of Libya can remove their dictator, but we are not going to be the ones who remove him," he said.
Senator John McCain, the 2008 Republican U.S. presidential nominee, criticized Obama, saying he had not clearly explained the goal of the U.S. military operation in Libya and should do so in a televised address scheduled for Monday.
"This policy has been characterized by confusion, indecision and delay," McCain told "Fox News Sunday." "It's no wonder that Americans are confused as to exactly what our policy is because on one hand they say it's humanitarian on the other hand they say Gaddafi must go." (Reporting by Arshad Mohammed; Editing by Anthony Boadle and Sean Maguire)