The White House Friday said it had been motivated by shielding Syrian civilians, Israelis and its own security, when President Barack Obama nixed an administration plan to arm Syrian rebels.

Defense Secretary Leon Panetta said during a congressional hearing Thursday that he backed plans to arm and train vetted rebel groups fighting President Bashar al-Assad's forces, in an initiative also supported by former secretary of state Hillary Clinton and ex-CIA chief David Petraeus.

But White House spokesman Jay Carney argued Friday that the problem in Syria was not a lack of weapons, hinting that rebels were getting sufficient supplies from other regional powers and Assad was getting help from outsiders like Iran.

Carney said that the US priority was to ensure that weapons provided by Americans did not end up in the wrong hands and to create more danger for "the US, the Syrian people or for Israel."

Panetta's admission angered some lawmakers keen to provide more US support to Syrian rebels, including Republican hawk Senator John McCain.

It also sparked speculation of a split in Obama's cabinet, and suggestions that the president was slow to support the Syrian people.

Carney declined to get into internal administration deliberations over Syria policy, which he said was constantly under review, and did not boil down to one simple decision.

The Obama administration has declined to provide anything other than humanitarian or non lethal aid to Syrian rebels, including communications equipment.

The administration appears concerned that in the eventual post-Assad Syria, some rebel groups could turn to militancy and extremism armed with US-provided weapons.

The rationale for providing weapons under the Petraeus scheme centered not simply on a desire to tip the balance against Assad, but to give the United States influence with groups that control the country should he fall.

The New York Times reported Friday that the Petraeus scheme failed to come to fruition, partly because its author resigned over a sex scandal and Clinton missed many of her final weeks on the job with concussion.