By Phil Stewart and David Alexander
WASHINGTON (Reuters) - The United States is rethinking its opposition to arming the Syrian rebels, President Barack Obama's defense chief said on Thursday, even as Obama himself signaled that no decision to deepen U.S. involvement in the conflict was imminent.
Defense Secretary Chuck Hagel cautioned that giving weapons to the forces fighting President Bashar al-Assad was only one option being considered by the United States. It carries the risk of arms finding their way into the hands of anti-American extremists among the insurgents, such as the Nusra Front.
But it may be more palatable to many in the United States than direct U.S. military intervention in the conflict, such as carving out a no-fly zone or sending in troops to secure chemical weapons.
Asked whether the Obama administration was rethinking its opposition to arming the rebels, Hagel said, "Yes."
"You look at and rethink all options. It doesn't mean you do or you will" choose them, Hagel told a Pentagon news conference.
Obama, speaking in Mexico, said the United States would "look at all options." But he also signaled no decision would be rushed.
"We want to make sure that we look before we leap and that what we're doing is actually helpful to the situation, as opposed to making it more deadly or more complex," Obama said.
Pressure on Obama to act on Syria has grown since the disclosure of U.S. intelligence that Assad's forces likely used chemical weapons on a small scale, particularly sarin gas.
The Syrian government has also mounted a string of attacks reaching from the capital, Damascus, and the central city of Homs out to the Mediterranean coast, homeland of the Alawite minority sect to which Assad himself belongs.
Forces loyal to Assad stormed the coastal village of Baida on Thursday, killing at least 50 people, including women and children, the Syrian Observatory for Human Rights said.
An Obama administration official, speaking on condition of anonymity, said re-examining the option of arming the rebels was part of a broad look at ways to hasten an end to the conflict, which has cost more than 70,000 lives and forced refugees to flee to U.S. allies Turkey and Jordan.
"Does that mean that they (arms) will be provided? No, it means we're reviewing all options to see how we can accelerate the transition in Syria," the official told Reuters.
Most Americans do not want the United States to intervene in Syria's civil war even if the government there uses chemical weapons, a Reuters/Ipsos poll showed on Wednesday.
British Defence Secretary Philip Hammond, speaking alongside Hagel, noted that his government was constrained by a European Union ban on supplying armaments to the rebels.
"Both of our nations will only do what we legally can do," Hammond said, adding his government would "look at the situation when that ban expires in a few weeks' time."
The Obama administration would be extremely reluctant to authorize any intervention involving a large-scale U.S. ground force, and Hagel warned of the risks of Americans being mired in a broad, regional conflict.
The Pentagon has developed plans, however, to potentially deploy troops if needed to secure Syrian chemical weapons sites.
"Any kind of boots-on-the-ground scenario like Iraq is not likely at all," the U.S. official said.
Indeed, the United States has resisted being dragged militarily into Syria's conflict and is providing only non-lethal aid to rebels trying to overthrow Assad.
The U.S. official denied that looking again at possibly arming the rebels was being done in response to the intelligence assessment of Syria's likely use of chemical weapons.
The White House has not specified what evidence it has that Syrian forces used sarin, but U.S. government sources said it included samples of blood from suspected victims, and of soil.
Obama has called any confirmed use of such weapons a "game changer," but said last week the evidence was only preliminary and that he would not allow himself to be pressured prematurely into deeper intervention in Syria's two-year-long civil war.
Hammond noted that any evidence of chemical weapons use would need to be at a very high legal threshold to justify military action - particularly with memories still fresh from the Iraq war.
Then, faulty intelligence was used to justify the Iraq invasion in pursuit of nuclear, chemical and biological weapons that turned out not to exist.
Asked whether it might take another chemical weapons attack before the United States and Britain could gather the right kind of evidence, Hammond said it was not that they "necessarily would need" a new attack, even as he acknowledged that evidence of chemical weapons use degraded with time.
"But clearly, if there were future use of chemical agents, that would generate new opportunities for us to establish a clear evidence of use to a legal standard of evidence," Hammond said.
"There is a very strong view that we have to have very clear, very high-quality evidence before we make plans and act on that evidence."
Ake Sellstrom, the Swedish scientist leading a U.N. inspection mission charged with investigating allegations of chemical weapons attacks in Syria, met U.S. chemical weapons and regional experts at the State Department on Thursday.
U.N. chief Ban Ki-moon said on Monday the investigators had been gathering and analyzing available information on alleged chemical weapons attacks in Syria but that access to the war-torn country was needed for a "credible and comprehensive inquiry."
Syria has blocked unconditional and unfettered access by the U.N. mission, which has an advance team in Cyprus ready to deploy to Syria within 24 to 48 hours, and it is unlikely it will gain that type of access any time soon.
(Additional reporting by Matt Spetalnick, Arshad Mohammed and Mark Felsenthal; Editing by Peter Cooney)