In statements before the informal talks of the EU defense ministers, Mugrinni called for "constructive action" to continue the mission.

"So far no consensus has been reached," she said before the meeting in Vienna. "We can not leave the EU process without clarifying the rules to follow. It would be good for member states to assume more responsibility. It is important that we keep the process going. It is a great achievement for all EU countries," she added.

Rome plans to ask the EU to amend the rules of Sofia's mission - currently led by Italy - and to rotate the ports of landing of rescued migrants in the Mediterranean, with the expectation that France and Spain will be at the head of the countries that will be asked to receive immigrants.

At present, all ships carrying rescued migrants are anchored in Italy, but Italy's new right-wing government says it should not shoulder the burden alone and that the time has come for other EU countries to shoulder their share of immigrants.