The Reuters news agency described the US State Department statement as the sternest warning since Russian mercenaries were first seen in Tripoli in September.
The agency quoted, diplomats and officials in Tripoli, that Hifter supported by Egypt and the United Arab Emirates, and that mercenaries from Russia have offered support to him recently.
Reuters pointed to the US call to Hofter to halt his offensive on the internationally recognized government-controlled capital Tripoli and warned of Russian intervention.
The State Department has called in a statement Friday, after a security dialogue between the United States and the delegation of the Government of National Accord headed by Interior Minister Fathi Pashaga, in Washington, the forces of “Hifter” to end its offensive on the capital Tripoli.
