U.S. plans to arm Syrian rebels passed one congressional hurdle but may face more when funding runs out in two months, further delaying the flow of weapons, U.S. officials and other sources said.
House and Senate intelligence panels this month agreed to a White House plan to provide arms to rebels fighting to topple Syrian President Bashar al-Assad, despite lawmakers' reservations about the its chances of success.
But a U.S. official involved in the issue said funding for the classified program runs out on September 30, the end of the government's fiscal year. That means the White House will again have to seek Congress' blessing for arming the rebels, the official said, possibly setting up a renewed confrontation over Washington's policy in the Syrian civil war.
Obama administration representatives have told Congress they are setting up a mechanism to vet rebels - including interviews - before handing over weapons, which could also lead to delays.
Sources close to the Syrian rebels said they fear the American arms delivery will be a drawn-out process in which they get a modest amount of arms in an initial tranche, and congressional committees will have to approve more later.
Despite their approval of the White House plan, several U.S. lawmakers expressed doubts on Tuesday that increased American support will be enough to help rebels turn the war's tide, which has shifted sharply to Assad's Iranian-backed forces.
There is also deep concern that the arms could end up in the hands of radical Islamist fighters who are among the rebels' strongest factions.
"Increasingly, I believe senators on both sides of the aisle want more information about what the end game is here," said Senator Ron Wyden, a Democrat like President Barack Obama.
Others questioned whether the arms will be too little, too late to help Syria's armed opposition against Assad forces buttressed by Iranian-backed Hezbollah fighters.
"I don't know if it moves quickly or slowly, it won't change the battlefield situation. Light weapons don't do well against tanks and airplanes," said Senator John McCain, a Republican who backs more aid for Syrian rebels. "What they are doing is meaningless."
U.S. Representative Michele Bachmann, a Republican on the House Intelligence Committee, said she had not been aware that the panel had agreed the White House could move forward.
"It was made to look as though there is a quote 'consensus' of the committee," she told Reuters. "I did not agree to this in any way."
Bachmann predicted U.S. support would end up aiding Islamist rebel groups that are sympathetic to al Qaeda.
"And now we're actually going to overtly, intentionally, fund jihadists?" she said. "This is beyond madness."
(Additional reporting by Tabassum Zakaria; Writing by Warren Strobel; Editing by Alistair Bell and Doina Chiacu)
(This story was refiled to add dropped word rebels in the 10th paragraph)