Italy says it is waiting for other European nations to pledge to take some of the hundreds of migrants on board before allowing them to step on to Italian soil.
The Czech Republic has rebuffed the appeal, calling the distribution plan a “road to hell”.
Italy has vowed to prohibit further disembarking of migrants who were rescued unless the burden is shared by other EU countries.
Both Italy and Malta have blocked aid groups from operating rescue boats, either by refusing them entry to their ports or by impounding their vessels and putting their crews under investigation.
The UN migration agency, meanwhile, said the number of migrants and refugees who have arrived in Spain by sea this year has overtaken those who have reached Italy.
The International Organisation for Migration said on Tuesday that Spain saw 18,016 migrants up to 15 July, while 17,827 people landed in Italy during the same period.
Aid groups have reported a rise in the number of crossings to Spain and Greece compared to the previous year, while arrivals in Italy are down almost 80 percent from 2017.
The overall number of migrants and refugees entering Europe by sea this year totals 50,872, less than half the 109,746 who came in by mid-July last year.
In 2016 during the same period, 241,859 migrants came to Europe.
IOM also said 1,443 people are dead or missing in the dangerous Mediterranean Sea route up to 15 July this year.