WASHINGTON – As one diplomatic effort after another fails to end more than a year of brutal violence in Syria, the Obama administration is preparing a plan that would essentially give U.S. nods of approval to arms transfers from Arab nations to some Syrian opposition fighters.

The effort, U.S. officials said, would vet members of the Free Syrian Army and other groups to determine whether they are suitable recipients of munitions to fight the Assad government and to ensure that weapons don’t wind up in the hands of al-Qaida-linked terrorists or other extremist groups such as Hezbollah that could target Israel.

The plan, which has not yet been finalized, reflects U.S. frustration that none of the previous efforts — including diplomatic rhetoric from the United Nations and the multinational Friends of Syria group, and special envoy Kofi Annan’s plan for a cease-fire — has even begun to nudge President Bashar al-Assad from power. The vetting would be the first tiny step the United States has made toward ensuring that the Syrian opposition uses the weapons to fight Assad and not to turn it into a full sectarian conflict.

While some intelligence analysts worry that there may be no suitable recipients of lethal aid in the Syria conflict, the vetting plan has arisen as the least objectionable idea in a complicated situation.

U.S. officials, most of whom spoke on condition of anonymity because of the sensitive nature of the subject, stressed that the United States, which is already providing non-lethal aid to Syria’s political opposition, is not supplying military assistance to Assad’s foes.

The administration’s position remains that adding more weapons to the conflict is a bad idea and will only fan the fire of instability.

“We don’t think that adding fuel to this fire is the right way to go,” State Department spokeswoman Victoria Nuland said.

“Our decision is to support the civilian opposition in nonlethal ways,” she said. “There are other countries who have made other decisions. That’s their sovereign decision to make. We’ve made our decision.”

But she added: “We are obviously consulting with various states about the decisions that we’ve made, that they’ve made.”

Privately, officials say that as conditions continue to deteriorate, it would be irresponsible not to weigh in with Arab countries such as Saudi Arabia, Qatar, the United Arab Emirates and others such as Turkey that have indicated interest in arming the rebels.

By some accounts, those nations already have begun to ship weapons with tacit U.S. agreement. In Turkey, private businessmen have begun funneling weapons into Syria.