WASHINGTON (Reuters) - While still solidly behind Pakistani President Pervez Musharraf, the United States appears to be bracing for the possibility that he might have to give up or share power, analysts said.

An ally in the U.S.-led war on terrorism, Musharraf has seen his popularity erode this year following a failed attempt to oust Pakistan's chief justice and a series of bombings and clashes across the nuclear-armed South Asian nation.

While analysts said Washington was by no means abandoning Musharraf, a general who seized power in bloodless 1999 coup, his diminished popularity and Pakistan's pro-democracy clamor appear to have made the United States consider contingencies.

"Their preference would certainly still be that Musharraf continue. They are comfortable working with him and they probably consider him a stronger leader than the alternatives," said Teresita Schaffer of the CSIS think tank.

"But I think they would like to see him joined to one or another of the secular parties because they think that provides a stronger combination," she added. "That is a recalibration, but I don't think they would characterize it as moving away from Musharraf because they still want him."

Ten days ago, a diplomat said Washington had urged Musharraf to explore ways of cooperating politically with former Prime Minister Benazir Bhutto, whose father, also a Pakistani leader, was executed during a previous period of military rule.

The effort to encourage a political deal, first reported by The New York Times, appeared aimed at shoring up Musharraf's domestic support and ensuring Pakistan's continued cooperation with the United States in the war on terrorism.

The strategy carries risks for Washington, which could be seen as meddling in Pakistan's internal affairs, and for Bhutto, who could taint herself by allying with Musharraf, the latest of a long line of military officers to rule Pakistan.

Last week, Pakistan's Supreme Court ruled that another former prime minister, Nawaz Sharif, whom Musharraf ousted in 1999, could return to Pakistan after seven years in exile.

There is no love lost between the two. Pakistan's military overthrew the former prime minister after he sought to replace Musharraf as army chief of staff while the general was out of the country.

Analysts said the prospect of Sharif's return was sure to raise domestic pressure on Musharraf, who hopes to win a second term as president in an election expected to be held this autumn. Fresh parliamentary elections are expected afterward.


'NOT WALKING AWAY FROM MUSHARRAF'

A senior U.S. official denied any effort by the United States to distance itself from Musharraf, who chose after the Sept. 11, 2001, attacks to support Washington in its effort to topple the Taliban regime in Afghanistan that harbored al Qaeda.

While declining to detail U.S. contacts with Sharif or Bhutto, the official said contact with opposition parties was natural ahead of Pakistan's elections.

"We're not walking away from Musharraf," the U.S official said flatly. "We're just talking to more people because it's a political year and more people are coming up in importance."

"We are trying to help him make a successful transition because he knows and we know that is the only way to continue the alliance ... and to continue moving the country in the direction he's charted," he added.

Stephen Cohen, an analyst at the Brookings Institution think tank, said he thought the U.S. emphasis in recent months on the importance of Pakistan holding free and fair elections bespoke a slight shift in the U.S. approach.

"We hadn't been talking about that at all, or if we had, it was in the most abstract way," Cohen said. "I think that's language that probably reflects an adjustment in policy -- not a change -- but an adjustment to support Musharraf, but to be prepared if things go in different directions."

Lisa Curtis of the Heritage Foundation think tank said U.S. officials had been "somewhat behind the curve" in grasping how much Musharraf's standing had diminished and how strong the pro-democratic sentiment was in Pakistan.

"The political landscape has changed drastically inside Pakistan over the last six months, with Musharraf's popularity plummeting, and I think the administration understands that and is now seeking to adapt its policy accordingly," Curtis said.

"Given the severe strains in the U.S.-Pakistan relationship, I believe it is critical that the administration not be seen as solely supporting Musharraf against the will of the people, who are obviously clamoring for democratic rule," she said.