By Ross Colvin and Caren Bohan
WASHINGTON (Reuters) - The White House pushed back on Monday against rising pressure from some lawmakers for direct intervention in Libya, saying it first wanted to figure out what various military options could achieve.
"It would be premature to send a bunch of weapons to a post office box in eastern Libya," said White House spokesman Jay Carney. "We need to not get ahead of ourselves in terms of the options we're pursuing."
Officials cautioned that a "no-fly" zone over Libya, an idea popular among Democratic and Republican lawmakers, would be difficult to enforce and might not stop helicopter gunships from attacking rebels fighting to end Muammar Gaddafi's four-decade rule.
The Obama administration has faced sharp criticism, especially from Republicans and conservative commentators, for being too cautious over the turmoil in Libya but has signaled it will not be rushed into hasty decisions that could suck the U.S. military into a new war and fuel anti-American sentiment.
One major obstacle: U.S. officials are still trying to identify the main actors within the opposition fighting to oust Gaddafi. The aims of these groups are unclear and it is not even certain they view the United States favorably.
Carney said the United States was trying to "reach out" to Gaddafi opponents through diplomats, business people and non-governmental groups.
He also had a fresh warning to Gaddafi's close associates, saying U.S. intelligence agencies were seeking to identify those involved in the violence which has forced tens of thousands of people to flee the country.
President Barack Obama said he wanted to "send a very clear message to the Libyan people that we will stand with them in the face of unwarranted violence and the continuing suppression of democratic ideals that we've seen there."
But Kori Schake, an associate professor at West Point military academy, was critical of Obama's statement, saying it followed a "pattern of broad pronouncements without practical follow-through."
The White House has long said all options are on the table over Libya but, for the first time on Monday, it gave a vague priority to the possible military steps being studied.
Bottom of the list is sending in ground troops, Carney told a briefing. Enforcing a no-fly zone was a "serious" option, he said, as was a U.N. arms embargo and humanitarian assistance.
Arming the rebels was also a possibility, he added.
But State Department spokesman P.J. Crowley appeared to contradict Carney when he noted that a February 26 U.N. Security Council resolution barred all weapons transfers to Libya.
Crowley also denied a British newspaper report that Washington had asked Saudi Arabia to supply weapons to rebels.
Military analysts say the rebels do not appear to be short of weapons and the United States would be wary of providing arms that could end up in the wrong hands and be used against U.S. forces elsewhere.
Brian Katulis, a Middle East expert who has informally advised the White House on the turmoil sweeping the region, said the Obama administration was constrained by its reluctance to act militarily without international support.
Defense Secretary Robert Gates reiterated on Monday that any intervention in Libya would require broad backing.
Underscoring the lack of consensus, Russian Foreign Minister Sergei Lavrov said Moscow opposed military intervention. China, a fellow veto-wielding member of the U.N. Security Council, has expressed similar misgivings.
The United States has deployed two amphibious assault ships off the Libyan coast, ostensibly to help with any humanitarian emergencies, while dispatching military transport aircraft to airlift stranded Egyptian refugees from neighboring Tunisia.
Over the weekend, leading Republican and Democratic senators urged Obama to do more to help Libya's rebels, who have fought Gaddafi's security forces to a standstill in some areas but are all but powerless to stop repeated air strikes.
Mitch McConnell, the top Republican in the Senate, said one option was "simply aiding and arming the insurgents," noting that the United States often did this during the Cold War.
John Kerry, the influential Democratic chairman of the Senate Foreign Relations Committee who is close to Obama, repeated his call for a no-fly zone and floated another idea -- bombing Libyan runways to ground Gaddafi's warplanes.
(Additional reporting by Caren Bohan, Phil Stewart, Matt Spetalnick, Andrew Quinn, Susan Cornwell and Patricia Zengerle; Editing by John O'Callaghan and Todd Eastham)