SINGAPORE (BLOOMBERG) - The Trump administration's stern warning to Libyan militia leader Khalifa Haftar to halt his forces' advance on Tripoli sent oil prices to their highest level in more than four months amid mounting supply concerns.
Secretary of State Michael Pompeo said in a statement late on Sunday that the US was "deeply concerned" about the warlord's threat to the internationally recognised 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," Mr Pompeo said. "There is no military solution to the Libya conflict."
Bent for June settlement advanced as much as 0.7 per cent to US$70.86 a barrel on the London-based ICE Futures Europe exchange, the highest since Nov 12.
Crude prices have continued to climb after their strongest quarter in almost a decade as Opec and its allies curb output while economic and political crises squeeze supplies from member nations Venezuela and Iran.
An escalation of the conflict in Libya, which pumped 1.1 million barrels of crude a day last month, risks creating a supply shortfall.
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," Mr Pompeo said.
The Opec member's internationally recognised government said it would counter-attack to clear Haftar's forces, which could lead to some of the bloodiest battles since the 2011 civil war that ousted strongman Muammar Gaddafi.
As tensions grow increasingly inflamed, so does the risk of disruption to Libya's oil production - fighting anywhere in the country, even if it's far from major oil fields, can cause swings in output.
The US Africa Command is temporarily withdrawing troops from Libya in response to "security conditions on the ground", the latest chapter in America's fraught military involvement in the North African country since Gaddafi fell.
Libya's government said in February that joint Libyan and US forces had bombed a site linked to Al-Qaeda militants in the south.
A 2016 US-backed campaign pushed local Islamic State in Iraq and Syria (ISIS) groups from their stronghold of Sirte.
But Libya needs more help from America to overcome its divisions and stop the militant organisation from regrouping amid the current chaos, Interior Minister Fathi Bashagha said last month.
Over the past year, ISIS has claimed several attacks, including at the elections headquarter, the Foreign Ministry and the National Oil Corporation's headquarters in Tripoli.
"It will be expensive for us as Libyans and expensive for the United States, which by its own laws is obliged to fight Al-Qaeda and Daesh," Mr Bashagha said in March, using the Arabic acronym for ISIS.
"The United States must pay more attention to the Libyan political file to make sure there is a political deal."