WASHINGTON — A cache of powerful American missiles was sold to France before ending up in the hands of rebel fighters loyal to Gen. Khalifa Hifter, who is seeking to overthrow the United Nations-backed government in Tripoli.

The four Javelin anti-tank missiles, which cost more than $170,000 each and are usually sold only to close American allies, were recovered last month by Libyan government forces during a raid on a rebel camp in Gheryan, a town in the mountains south of Tripoli.

A French military adviser denied on Tuesday that the weapons were transferred to General Hifter, which would violate the sales agreement with the United States as well as a United Nations arms embargo. It would also put Washington at odds over Libya policy with France, a staunch NATO partner and ally in other hot spots like West Africa.

Over the past several days, the State Department investigated the origins of the missiles, using their serial numbers and other information, and concluded that they had originally been sold to France, which has been a strong supporter of General Hifter. France agreed to buy up to 260 Javelins from the United States in 2010, according to the Pentagon’s Defense Security Cooperation Agency.