A report by the Wall Street Journal on Sunday revealed that the Pentagon is conducting investigations regarding the deep ties between Haftar and the mercenaries from the Wagner Group, a Russian firm with ties to the Russian government.
The newspaper quoted US officials as saying that Washington has threatened to sanction Haftar because of his refusal to reopen oil exports, saying the decision had been taken under Russian influence.
"The warlord initially allowed the ports to be reopened, but he changed his mind when the Wagner Group fighters moved to Es Sidr," the report added.
"The State Department has threatened Haftar with sanctions because he was acting silly and showed no flexibility," one official told the Journal.
According to American property records, Haftar owns a farm with a value of $ 185,000 and a residence of $ 364,000 in Virginia, which makes him liable to the US penalties, according to the Wall Street Journal.