The western city of Ghadames will host a long-awaited national conference aiming to unite Libya, but the balance of power has shifted. General Haftar’s asking price for a deal is now much higher.

Amid rumors of an imminent move on Tripoli by General Khalifa Haftar, UN envoy Ghassan Salame on 20 March announced a long-delayed Libyan national conference for 14-16 April that, if successful, would unite rival governments and set a way out of the seemingly unending eight-year transitional...