By Phil Stewart and Patricia Zengerle

WASHINGTON (Reuters) - Pentagon leaders told Congress on Thursday that they had supported a recommendation to arm Syrian rebels promoted by the State Department and CIA but which President Barack Obama ultimately decided against.

Obama's government has limited its support to non-lethal aid for the rebels who, despite receiving weapons from countries like Qatar and Saudi Arabia, are poorly armed compared to Syrian President Bashar al-Assad's army and loyalist militias.

Syria's 22-month-long conflict has killed an estimated 60,000 people.

Senator John McCain, a Republican from Arizona, has championed greater U.S. involvement and chided the Obama administration at a hearing, asking Pentagon leaders: "How many more have to die before you recommend military action?"

He then pressed Defense Secretary Leon Panetta and General Martin Dempsey, the chairman of the U.S. military's Joint Chiefs of Staff, about whether they backed the recommendation by the State Department and CIA chiefs last year to arm the rebels.

Panetta and Dempsey said they had backed the recommendation, and later in the hearing, the defense secretary elaborated.

"Obviously there were a number of factors that were involved here that ultimately led to the president's decision to make (the aid) non-lethal," Panetta said, adding he supported Obama's decision.

The comments were the first public acknowledgement of Pentagon support to arm the rebels since the New York Times reported on February 2 about the plan developed last summer by Hillary Clinton and David Petraeus, who have since left their jobs at the State Department and CIA, respectively.

The defense chiefs' testimony also suggested that White House opposition alone may have been enough to override the position of most major U.S. foreign policy and security agencies - the State and Defense departments, and the CIA.

CONCERN ABOUT DEEPER U.S. INVOLVEMENT

The Times said that the plan to arm and train rebels was rebuffed by the White House over concerns it could draw the United States into the Syrian conflict and that the arms could fall into the wrong hands.

The questions about U.S. policy in Syria came during a hearing focusing on Libya, with Pentagon leaders defending their response to last year's deadly attack on the U.S. consulate in Benghazi.

Republican lawmakers raised questions about whether the reaction was too slow and whether Obama was not engaged enough during the incident, choosing to get updates on the crisis from staff instead of military leaders. Continued...