The United States has begun a long-awaited program to train Syrian fighters to go into combat against Islamic State, the Pentagon said on Thursday, deepening America's role in Syria's civil war after eight months of airstrikes against the Sunni militants.

Defense Secretary Ash Carter said the military was starting small, training a first group of just 90 Syrians, who would be paid a stipend and could expect some still-undefined support once they return to the battlefield.

A spokesman for the government of Jordan said the training began there several days ago and U.S. and Middle Eastern sources told Reuters the training would soon start at another site in Turkey.