A ship carrying 40 migrants, including two pregnant women, has been stranded for two weeks in the Mediterranean after four countries refused it permission to dock.

The Tunisian-flagged offshore supply vessel, the Sarost 5, is currently three kilometres from Zarzis on the southeastern Tunisian coat, the ship's second-in-command, Aymen Ourari, said.

The ship is the latest to be caught up in the diplomatic deadlock over what to do with migrants rescued from the Mediterranean: Malta, France, Italy and Tunisia have all rebuffed requests for it to dock.

Ourari told CNN that if the Sarost is forced to remain at sea, the 14-strong crew foresees “serious incidents” for those on board, who have “about three or four days’ worth of food” among them.

The international humanitarian agency the Red Crescent visited the boat Wednesday, Ourari said, describing the situation as a “health crisis.”

The 40 migrants were picked up on July 13 from a wooden boat that got into difficulties while attempting to cross the Mediterranean from Libya.

International Federation of Red Cross and Red Crescent Societies spokesman Matthew Cochrane told CNN that its doctors managed to get on the boat earlier this week to assist people in poor health conditions and provide food and water.

“We addressed the most pressing needs of people on board but this is clearly not sustainable. People have a right to be treated with dignity and respect,” he said.

The European Commission said earlier this week it would give EUR 6,000 to member states for every migrant disembarking from the Mediterranean, in an effort to break the impasse over the issue. But there is no sign of a solution for those on board the Sarost 5.

Malta denied that it should have taken the migrants. In a statement on July 19, Malta rejected claims that it illegally directed the boat into Tunisian territorial waters.

A spokesperson for the French Maritime Prefecture of the Mediterranean declined to comment on whether the ship was prevented from docking in France, pointing to a lack of authorization to provide information on matters related to migration.

CNN also contacted the governments of Tunisia and Italy but has yet to receive a response.