Speaking in Washington, Rodriguez said "a couple of hundred" militants are undergoing training and that the United States is "watching them carefully to see how it develops." He added he has not recommended that U.S. airstrikes target the camps.
"We'll have to just continue to monitor and watch that carefully in the future, to see what happens or whether it grows unabated," he said.
Libya has been without central government authority since the overthrow of Muammar Ghadafi's regime in 2011, and the country is controlled by a variety of competing militant groups, some aligned with IS. It is believed many Libyan rebels left to fight in Syria and have returned home.