(Bloomberg) -- The Trump administration issued a stern warning to Libyan militia leader Khalifa Haftar to halt his forces’ advance on Tripoli, and urged all aides to continue with political negotiations.

Secretary of State Michael Pompeo said in a statement late Sunday that the U.S. was “deeply concerned” about the warlord’s threat to the internationally recognized capital. He said the military campaign was endangering civilians and undermining efforts to resolve the dispute peacefully.

“We have made clear that we oppose the military offensive by Khalifa Haftar’s forces and urge the immediate halt to these military operations against the Libyan capital,” Pompeo said. “There is no military solution to the Libya conflict.”

Haftar is moving his self-styled Libyan National Army west to Tripoli to fight what he says is “terrorism,” after solidifying control of the east and sweeping through the south in January. Clashes have continued on the outskirts of the capital, including air strikes, despite appeals by global powers to halt the offensive.

“A political solution is the only way to unify the country and provide a plan for security, stability and prosperity for all Libyans,” Pompeo said Sunday.

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