France is not ready for now to let the Mediterranean rescue ship Aquarius dock and disembark dozens of migrants at the port of Marseille but suggested it do so in Malta, according to government sources.

"For the moment it's 'no'," finance minister Bruno Le Maire said when asked on BFM TV if Paris was ready to respond positively to a request from charities for permission to dock with 58 people aboard in the southern French port.

Mr Le Maire said ships were supposed to dock at the nearest port under European rules and Marseille was not the nearest.

"On matters of migration, the issue must be handled firmly and clearly, and European rules respected," the minister said.

Instead, France is pushing for Aquarius to dock in Malta and unload the 58 migrants on board, a source in the presidential office told AFP.

"We are clear on the fact that it shouldn't spend four to five days at sea going towards France ou Spain or anywhere," the source said on condition of anonymity. "It needs to dock soon and it is close to Malta at the moment."