Libya unity government accuses rival Haftar of seeking coup
"It's a farce and the latest in a long series of coups d'etat," the Government of National Accord (GNA), which is based in the capital Tripoli, said in a pre-dawn statement.
The oil-rich North African nation has been gripped by chaos since the ouster and killing of longtime dictator Muammar Gaddafi in 2011, with rival administrations in the east and west vying for power.
Haftar, who controls swathes of eastern Libya and in April last year launched an offensive to seize Tripoli, on Monday said his self-styled "army" had "accepted the will of the people and its mandate".
The military commander did not make clear, however, if a parliament elected in 2014 and also based in the east of the country backed his move.
Haftar claims his legitimacy from that parliament which was forced to move its headquarters after violence ripped apart Tripoli six years ago.
The GNA said Haftar had "turned his back on the parallel political institutions that backed him and designated him" head of the army.
Washington called for dialogue between the two sides and a "humanitarian" truce.
"The United States regrets... commander Haftar's suggestion that changes to Libya's political structure can be imposed by unilateral declaration," a statement on its embassy's Twitter account said.
"As civilians continue to suffer during the holy (fasting) month of Ramadan and the COVID-19 pandemic threatens more lives, we urge the LNA (Haftar's forces) to join the Government of National Accord in declaring an immediate humanitarian cessation of hostilities," it said.
Haftar has been accused by his detractors of seeking to impose a new military dictatorship in Libya.
On Monday he announced the "end" of a 2015 UN-mediated agreement that produced the GNA.
He made similar remarks in 2017 and three years earlier also appeared on television to say that he was taking the reins of power in Libya.
Haftar's offensive to seize Tripoli has claimed hundreds of lives and displaced some 200,000 people.
Agencies contributed to this report.