Signed by the EU's High Representative Josep Borrell and Foreign Ministers Jean-Yves Le Drian of France, Heiko Mass of Germany and Luigi Di Maio of Italy, a statement urged "all Libyan and International parties to effectively and immediately stop all military operations."
The European ministers also insisted on the need to "engage constructively in the 5+5 negotiations" in reference to a joint military commission that helped broker a ceasefire announced in Cairo earlier this month.
Meanwhile, international efforts must include "the withdrawal of all foreign forces, mercenaries and military equipment supplied in violation of the UN arms embargo from all regions of Libya", the joint statement said.
The Libyan ceasefire has been backed by strongman Khalifa Haftar and was to have taken effect on Monday.
But forces loyal to Libya's Government of National Accord (GNA) have declared their aim to take Sirte, the hometown of slain dictator Muammar Qadhafi, and build upon a string of recent successes against Haftar's men.
The joint statement urged those fighting in Libya "to engage constructively in all strands of the UN-led intra-Libyan dialogue in order to pave the way for a comprehensive political agreement in accordance with the parameters agreed upon in Berlin."
On January 19, the main countries involved in the Libyan conflict agreed in Berlin to respect an arms embargo and to stop interfering in Libya's domestic affairs.
Libya has been mired in chaos since the 2011 uprising that toppled and later killed longtime dictator Muammar Qadhafi.
Eastern-based Haftar has since last year sought to regain control over the west, fighting the GNA in an abortive attempt to seize the capital Tripoli