US recruits 'about 60' Syrians to fight IS
In January, the Pentagon said about 5,400 Syrian rebels would be trained and armed in the first year of the project, and US lawmakers allocated $500 million to the programme - which, along with airstrikes, is a central tenet of Washington's strategy to beat the IS group.
"This number is much smaller than we had hoped for at this point," he added, pointing to difficulties in vetting suitable candidates.
"We know this programme is essential. We need a partner on the ground in Syria to assure ISIL's lasting defeat."
Rebels unhappy with US conditions
|This reason was not convincing for me. So we said no.
- Mustapha Sejari
Last month it was reported that around 150 so-called "moderate" Syrian opposition fighters had left the training programme - they objected to being required to pledge not to attack the Syrian regime with the weapons and training they were being given.
Talking to The Daily Beast, Mustapha Sejari, who claimed to be the commander of 1,000 fighters, said a Department of Defense liaison officer told him they were given the money from Congress for a programme to fight the IS group only.
"This reason was not convincing for me. So we said no," said Sejari.
"[My men] don't want to be beholden to this policy because it can be used against them in Syria - that they've betrayed the revolution and now they're just mercenaries for the coalition forces."
The Pentagon denied the Training and Equip project trainers had ever worked with the commander.
|Read more: US-trained rebels reject pledge not to attack Syrian regime|
Criticism of US strategy
The disclosure of the low number of fighters being trained is likely to add to criticism of the Obama administration's military strategy, with US Senator John McCain saying that the United States was "losing" the fight against the extremists, who have overrun large areas of Syria and Iraq.
"There is no compelling reason to believe that anything we are currently doing will be sufficient to achieve the president's long-stated goal of degrading and ultimately destroying ISIL - either in the short-term or the long-term," McCain told the Senate Armed Services Committee.
"Our means and our current level of effort are not aligned with our ends. That suggests we are not winning, and when you are not winning in war, you are losing."