(Adds comments by U.S. defense secretary, paragraph 13)
By Steve Holland and Lesley Wroughton
WASHINGTON, Feb 18 (Reuters) - Despite a forthcoming review of options in the deteriorating Syria crisis, the White House on Tuesday signaled that President Barack Obama remains wary of any direct U.S. involvement in the three-year-old civil war.
U.S. policy toward Syria appears to be approaching a crossroads, with peace talks between Syrian President Bashar al-Assad's government and his armed opponents having failed for now and Russia unwilling or unable to pressure its ally Assad to cede power.
The White House is beginning to take a new look at options in Syria, a process that could take several weeks, U.S. officials have said.
But spokesman Jay Carney suggested Obama is skeptical about any proposed step that draws the United States into the Syrian civil war, an outcome Obama has studiously avoided.
"We have to examine what the alternatives some might be proposing are, and whether they're in our national security interests, and whether a desire to do something about it could lead us, the United States, to take action that can produce the kind of unintended consequences we've seen in the past," Carney told a news briefing.
He didn't elaborate but appeared to refer to Obama's desire to avoid getting caught up in another war in the Islamic world.
Short of military force, it is unclear how Washington can affect the course of the civil war, in which Assad is being supported by Iran and Russia.
Secretary of State John Kerry has argued at numerous White House meetings for a more aggressive stand on Syria, including arming opposition groups. The latter suggestion was repeatedly knocked down within the White House, current and former State Department officials said.
However, a senior administration official who briefed reporters before Obama's meeting on Saturday with Jordan's King Abdullah said expanded aid to the rebels is a possibility - but only if it nudges the sides toward a diplomatic solution.
A variety of other options remain on the table, including a "no fly" zone to protect civilians and measures to improve access for humanitarian relief.
Several officials said a review by U.S. government agencies of options on Syria had not officially started. The proposals would be narrowed down to two or three and submitted for review by Obama, the officials said.
Pentagon officials said the U.S. military was continuously reviewing Syria options, in case a need arose.
"Our role is to provide the president with options. We continue to do that. And we give the president our best, most honest advice," Defense Secretary Chuck Hagel said, adding the military was prepared to act if asked by Obama.
"RETHINKING" SYRIA POLICY
It was unclear what overt military steps might be politically palatable, given that last year many lawmakers balked at even limited military strikes in response to the Syrian government's alleged chemical weapons attacks in Damascus suburbs.
One Middle Eastern diplomat said Washington and its allies are concerned that Assad's confidence on the battlefield is undermining the now-stalled peace talks that have taken place in Switzerland.
The diplomat, speaking on condition of anonymity, acknowledged there is a "rethinking" of Syria policy in Washington, but played down any suggestion the United States is entertaining dramatic military moves that could oust Assad.
Kerry, speaking during a brief stop in Tunisia on Tuesday, said he had not given up on a diplomatic solution.
"The Geneva talks are an ongoing process. Nobody expected in two meetings or three meetings that this was going to be resolved," Kerry said, adding that he had talked to his Russian counterpart Sergei Lavrov by phone earlier in the day "to move the process."
The Obama administration had hoped that Russia would show more willingness to pressure Assad but there is a realization that that plan is not working, said a U.S. administration official, speaking on condition of anonymity.
U.S. officials say, however, it is possible a U.N. resolution to help relieve the humanitarian crisis in Syria could get through the U.N. Security Council, where Russia and China have used their veto power to shield Syria.
The 15-member council met informally on Tuesday to continue negotiations on a draft resolution to boost humanitarian access in Syria, where the United Nations says some 9.3 million people need help.
Russia initially refused to engage on a Western- and Arab-backed text before Moscow presented its own draft. The two texts have been merged, but the council is still trying to find common ground on key points, including a threat of targeted sanctions and cross-border aid access, diplomats said.
"We could conceivably reach agreement on a humanitarian resolution. I would not exclude that possibility," said a senior Obama administration official, adding a strong resolution was needed.
"Strong doesn't necessarily mean the threat of sanctions or the threat of force, but strong in terms of the obligations and expectations it would impose on the regime to improve humanitarian access," the official said. (Additional reporting by Phil Stewart in Washington and Michelle Nichols at the United Nations; Editing by Warren Strobel, Mohammad Zargham and Paul Tait)