Dozens of people have been killed since Haftar, the strongman behind a rival administration in eastern Libya, launched an assault last Thursday on Tripoli, home to the UN- and EU-backed unity government.
“I make a very strong appeal to Libyan leaders and in particular to Haftar to stop all military activities in this moment and to return to the negotiation table under UN auspices,” Mogherini said after talks with EU foreign ministers in Luxembourg.
Mogherini said the foreign ministers did not take any formal written conclusions on Libya but were united around a common interest.
“There is a clear consensus on the call to stop immediately all military actions inside Libya being it from Libyans, or hopefully not or never from external actors.”
The EU has supported efforts by the UN-backed unity government in Tripoli to stabilise the country following the overthrow of Moamer Kadhafi in 2011.
Brussels works closely with the Tripoli-based government to stop migrants crossing the Mediterranean to Europe, which in 2015 faced its worst migration crisis since World War II.