A top U.S. military commander for operations in the Middle East acknowledged on Wednesday that there are only four or five fighters left from the first group of 54 Syrian fighters that had been trained by the U.S. as part of a $500 million program.
What's more, there are only 100-120 fighters in three more classes currently being trained, Under Secretary of Defense for Policy Christine Wormuth told the Senate Armed Services Committee on Wednesday.
The U.S. military is conducting a broad review of the training program.
General Lloyd Austin, who leads the U.S. military's Central Command, said he expected the numbers of U.S.-trained Syrian rebels to grow over time. But he acknowledged the program was behind schedule and the military's initial training targets would not be met.
The revelation sheds light on numbers that the Pentagon and U.S. Central Command have refused to provide the media for weeks, citing operational security.
Related: ISIS Fight: U.S. Says It Has Begun Training Syrian Fighters to Take On Militants
Earlier this year, Secretary Ashton Carter confirmed that the U.S. was training Syrian forces to fight ISIS, calling those efforts a "critical and a complex part" of U.S. efforts to fight ISIS.
Carter declined to say where they were being trained. He said that the rebels were being trained only to fight ISIS and were not being asked by the United States to fight the forces of President Bashar Assad in the Syrian civil war.
"These trainees are recruited, they're vetted, and only then are they put into training," he said. "So they've been in the program for quite a while."
President Barack Obama said in September that strengthening the Syrian rebels, rather than relying on Syrian government forces, represented the "the best counterweight" to ISIS militants.
In testimony before the Senate Armed Services Committee Wednesday, Austin revealed for the first time Special Operations Forces are "engaged with YPG" Kurdish forces. Austin did not elaborate.
Central Command later clarified that Special Operations is working with Kurdish forces in northern Iraq.
But Defense officials say those U.S. commandos are operating in an "advise and assist role" providing the basics on command and control and tactical operations. According to the officials, "those Special Operations Forces are not engaged in any combat operations" and are positioned far from the actual battle lines.
From the beginning of U.S. operations against ISIS in Iraq and Syria President Obama has pledged there would be no US "boots on the ground."
Austin also vowed Wednesday to take "appropriate action" if an investigation indicates that senior defense officials altered intelligence reports on the Islamic State and other militant groups in Syria to exaggerate progress being made against the terrorist groups.
A Defense Department inspector general began an investigation after an intelligence officer at the Central Command lodged a complaint in July. In his first remarks about the allegations, Austin told the Senate Armed Services Committee that he welcomed the Defense Department inspector general's investigation, but that he could not comment directly until the review was over.
Committee members expressed concern.
"Published media reports suggest that the CIA's estimate of ISIL's manpower has remained constant, despite U.S. airstrikes-which suggests that either they were wrong to begin with, or that ISIL is replacing its losses in real time. Neither is good," said committee chairman Sen. John McCain, R-Ariz.
"Indeed, this committee is disturbed by recent whistleblower allegations that officials at Central Command skewed intelligence assessments to paint an overly-positive picture of conditions on the ground," McCain said. He said the committee was investigating the allegations. "If true, those responsible must be held accountable," he said.
