One boat, the Lifeline, remained in limbo on Sunday with 239 Africans aboard, including pregnant women and children, with Malta and Italy refusing to take it in, after the Aquarius suffered a similar fate until it was allowed to dock in Spain.
On Saturday, another migrant rescue ship, the MV Lifeline, was waiting in the Mediterranean having been refused harbour by Italy and Malta.
Salvini has repeatedly accused the charities of being complicit with human smugglers.
But the German operators of the Lifeline hit out at Salvini for referring to its passengers as a consignment of "human flesh".
Sanchez said it was "important we have a common answer to a common challenge".
In France, almost 60% of the people are opposed to receiving migrants from Italy and Greece and an even bigger proportion agree that the Aquarius should not have docked in France.More news: Blood Moon 2018: Longest Total Lunar Eclipse of Century Occurs July 27
"We know that no solution will be reached on Thursday and Friday at the level of the 28 member states. on the overall issue of migration" she told a press conference during a visit to Beirut, Lebanon. In Brussels, Macron said "It's a political crisis mainly now".
In answer to comments by French President Emmanuel Macron, who said migration flows towards Europe had reduced compared with a few years ago, Italy's Deputy Prime Minister Luigi Di Maio said Macron's words showed he was out of touch.
The EU's top migration official on Monday urged European nations to work together to solve the migration crisis, ahead of a key summit in Brussels.
Macron has suggested, like Merkel, solutions by willing countries to make progress now since unanimity among the 28 member states will be hard. Four countries in Eastern Europe - the Czech Republic, Hungary, Poland and Slovakia - have refused to attend and reject taking in migrants in general.
Macron has infuriated Italy by accusing it of "irresponsibility" for turning away migrant vessels and denouncing the "leprosy" of rising populism.
Under the EU's so-called Dublin rules, asylum-seekers must be processed in the country where they first arrive, usually Italy, Greece and Spain.
Seehofer has threatened to defy Merkel and order border police from next week to turn back asylum seekers already registered in other European Union countries - unless Merkel reaches an agreement on how to handle them with other member states.More news: Ben Simmons named National Basketball Association rookie of the year
An asylum seeker from the Horn of Africa stands in a tented camp set up by the Baobad aid group, on the outskirts of Rome, Tuesday, June 19, 2018.
Macron said his proposal is "complementary" to one by EU Council President Donald Tusk that would put migrant centers for assessing cases in transit countries they used on the way to Europe.
Italy, the primary destination for the migrants, now has an anti-migration Eurosceptic government which turns back ships carrying rescued migrants.
In the latest crisis, her new hardline interior minister Horst Seehofer has given her until the end of June to find a European deal to curb new arrivals.
In a counter-proposal, Italy on Sunday called for migrant "protection centres" to be set up in several European Union countries to relieve overcrowding in its facilities and also demanded more aid for African countries that fight human trafficking. Meanwhile Spain's leader, Pedro Sánchez, called on "comrades" in other member states to help, following a recent spike in arrivals.
The EU struck the deal with Turkey in March 2016 and engaged Libyan coast guard in cracking down on migrant trafficking, following the peak year of 2015 which saw more than 1 million irregular migrants flocking to Europe.More news: Superhero suit complaints? Try wearing heels, Evangeline Lilly tells male co-stars