On Sunday, when Italy told the Aquarius not to proceed to ports in Sicily, Salvini first pushed Malta to accept the vessel, saying that the tiny European Union island country - in the middle of the Central Mediterranean migration corridor - routinely closes its doors.
Malta refused, saying it had nothing to do with the rescue mission, which was overseen by the Italian coastguard.
"In the Mediterranean.there's Malta that does now welcome anyone, there is France that rejects [refugees] at its borders, there's Spain that defends its borders with the arms".
The charity's spokesperson, Mathilde Auvillain, said the ship had received orders to head north and was now awaiting "definitive instructions".
"Italy doesn't shrug off its responsibility when it comes to saving lives, but it asks that others do the same", Transport Minister Danilo Toninelli, in charge of Italian ports and coast guard, said after the Spanish announcement. Malta said Italy coordinated the rescues and that the tiny island nation - which in the last few years has only accepted a few hundred migrants - has had nothing to do with it.
The Maltese Rescue Coordination Center "is neither the competent nor the coordinating authority", the statement said.More news: Vettel takes 50th win and F1 championship lead in Canada
When the Italian government took office last month, the big fear in Brussels was that it would use a threat to withdraw from the euro currency as a way to get what it wanted in Brussels.
The ship, Aquarius, is operated by Doctors Without Borders (MSF) and the SOS Mediterranee organizations.
In an attempt to ease the stalemate, a number of mayors of port cities in Italy on Monday said that they would allow the ship to dock in their cities. "Our sole objective is to bring the people we've rescued, in hard conditions yesterday, to a port of safety, ' the group said in a statement".
But Beau said that under maritime law the ship should be allowed to dock in one of the nearest countries, Italy or Malta.
Rescue at sea is regulated by worldwide law, which "is clear on the fact that any shipmaster has the obligation to provide assistance to persons in distress at sea", said Dr. Sarah Wolff, a lecturer in Public Policy at Queen Mary University, London.
As of June 6, there had been an estimated 785 deaths on the route this year, the IOM said, with the majority of the 33,400 migrants and refugees arriving through Greece and Italy.
Given that Italy's decision to close their ports was the first strong-man move from anti-immigration Home Affairs Minister and Leader of the League (LEGA), one of the two parties of the ruling coalition, and the murky waters surrounding worldwide obligations, it would appear that the stalemate may continue. Salvini campaigned on an anti-immigrant platform that included a vow to expel hundreds of thousands of migrants already in Italy, even though experts doubt such mass deportations are feasible or financially viable.