The fight against the Islamic State group received a jolt of energy when the United States and Turkey sealed a pact to train and arm Syrian rebels. Two months later, the program faces delays and skepticism — as Turkish officials, Syrian rebels and even former American advisers openly question whether it can ever have any battlefield impact.

The U.S. Defense Department says it is narrowing down a list of potential fighters to be trained under the $500 million U.S. program aimed at adding a credible ground force to the air bombing campaign already underway against IS. Turkish officials, who had initially pegged the start date to March, now say they are aiming for May.

Turkish officials say they have yet to hear the United States articulate a strategy for how the trained fighters will be deployed — or protected — in Syria. And while U.S. officials say they are keeping their strategy close to the chest so as not to give the enemy any clues, American analysts who have spoken to the planners are skeptical.

"My sense is that they do not have a real strategy in the sense of something that could actually achieve an objective," said Frederic Hof, who held ambassador status as the Obama administration's former adviser on the transition in Syria. Hof, now a fellow at the Washington-based Atlantic Council, called the program a placeholder in case the administration wants to ramp up the fight in Syria.

"I think the most it does now is that it checks a political box here in the United States, in the sense of providing talking points to the effect that you are actually doing something," said Hof.

He said that even the plan as it is articulated — regardless of whether it is properly implemented — holds little promise. The U.S. Defense Department has said it is aiming to train 5,000 Syrians a year for three years at a base in the central Anatolian city of Kirsehir as well as at sites in Saudi Arabia and Qatar. Those modest numbers raise doubts that the forces could survive in Syria long enough to weaken IS.

In addition to IS militants, the new recruits would likely face attacks from a Syrian government wary of a Western-backed force, as well as Islamic militants such as the al-Qaida-linked Nusra Front. But U.S. officials have resisted Turkish calls for the force also to be prepared to fight the government, while conceding that the recruits will have to defend themselves against all sides.

Joshua Landis, the director of the Center for Middle East Studies at the University of Oklahoma, said that U.S. officials argue that the conflict in Syria need not be a choice between Islamists on the one side and the Syrian government on the other. They suggest there is a third way with a moderate insurgent force — but he said such rebels have such a small constituency on the ground that they would have no chance without massive support.

"We are talking about arming the two percent," he said.

Turkish officials, speaking on condition of anonymity because of diplomatic sensitivities, said that the U.S. has not explained how the force can be effective on the ground in Syria. One official said the hope was that once the training began, the Obama administration would be forced to lay out a strategy.

Syrian rebels currently fighting in Syria are also skeptical. Officials with the Free Syrian Army, now the main Western-backed fighting force in Syria, said that the training is proceeding without adequate coordination.

Osama Abu Zayd, a legal counselor and adviser to the FSA, said there has been limited consultation so far, though some FSA representatives were recently briefed by U.S. officials on the content of the training. U.S. officials said they are working with individuals within the FSA, not the organization as a whole.

"We have a lot of questions about this training," said Zayd. "There is a lack of direct cooperation."

U.S. officials, speaking on condition of anonymity because of the sensitivity of the issue, said that the team under Lt. Gen. Michael Nagata in charge of choosing the rebels for training is looking at individuals rather than whole existing brigades — with a preference to adding fighters to the battlefield rather than taking people off it to boost their capabilities. The tactic reflects a sense among U.S. policy makers that the FSA has been ineffective and unreliable. The vetting team has been combing Syrian defectors currently in refugee camps for new recruits.

Zayd said that it will be hard to find hundreds of recruits who are not already with brigades, especially among those who have been sitting out the fight for their homeland.

FSA and Turkish officials have particular doubts about the chances of newly trained rebels to survive in Syria unless the U.S. provides protection. So far the U.S. has refused a Turkish proposal for enforcing safe areas and a no-fly zone in Syria. Without that, Turkish officials say, the recruits will be targeted from all sides, just as other U.S.-backed rebels have been.

In an indication of the challenges, the Hazzm Movement, once the most prominent CIA-backed group fighting in Syria, disbanded early last month after being overrun by Nusra. Some of the U.S. trained fighters ultimately joined Nusra, which also seized advanced anti-tank weapons provided by the CIA. A former adviser to Hazzm, who demanded anonymity because of fears his family in Syria could be targeted by Nusra, said the story should be a warning for the current U.S.-backed recruits.

After receiving the U.S. weapons, he said that Hazzm quickly became identified as a CIA-backed group. When U.S. President Barack Obama announced the U.S. air campaign in Syria in September and U.S. planes hit Nusra targets, Nusra in turn attacked Hazzm. Despite pleas for more support and weapons, the CIA's deliveries were sporadic and allies on the ground backed away because they saw Nusra coming.

"Hazzm found itself alone," the adviser said.