Italy's deputy prime minister has threatened to pull the country's EU funding if the bloc does not come to the aid of 150 people stranded aboard an Italian coastguard ship.
The migrants have been blocked at the Sicilian port of Catania on the Diciotti vessel since Monday night because the Italian government is refusing to allow them to disembark without commitments from the EU to take some of them in.
A meeting of high-level representatives from around a dozen EU member states is due to be held on Friday to discuss the issue, according to the Commission.
"In recent months we have had the chance to see how a soft line with the European Union worked and how a hard line works," Italy's Deputy Prime Minister Luigi Di Maio said in an interview published on Facebook on Thursday.
"If tomorrow (Friday) nothing comes out of the European Commission meeting, if they decide nothing regarding the Diciotti and the redistribution of the migrants, I and the whole Five Star Movement will no longer be prepared to give 20 billion euros ($23 billion) to the European Union every year."
EU figures for 2016 say Italy contributed just under 14 billion euros to the EU budget -- less than one percent of its gross national income -- while the bloc spent 11.6 billion euros in Italy.
Di Maio, who heads the anti-establishment Five Star, said Italy didn't want the "mickey taken out of us by the union's other countries" on the distribution of migrants.
"The EU was born of principles like solidarity. If it is not capable of redistributing 170 people it has serious problems with its founding principles," he said in an interview with state broadcaster RAI.
Friday's meeting follows Interior Minister Matteo Salvini's decision to leave the majority of the migrants on board the Diciotti after they were rescued on August 15.
His only concession has been to allow 27 unaccompanied minors off the boat Wednesday.
Migration is a hot-button issue in Italy, where hundreds of thousands of people have arrived since 2013 fleeing war, persecution and poverty in the Middle East, Africa and Asia.
Salvini said in an interview with Corriere Della Sera that the only way the migrants would be let off the Diciotti was "with a nice big airplane from one Europe's capitals landing in Catania".
"Europe needs to understand that the Italian government is irritated. We've had enough with their many words and few results," he said, claiming that the other nations had only taken in 12,000 of the 35,000 people they had promised.
Opinion polls suggest that Salvini's stance has boosted his far-right League party's approval rating to around 30 percent -- over 10 points up from its showing in the March election -- and is now level with the Five Star Movement with which it has governed Italy since the start of June.
However, according to Salvini's own ministry, migrant arrivals are more than 80 percent down on the same period last year, with just over 19,500 arriving up to August 23, compared to to 98,000 in 2017.
In an interview with La Stampa, European Investment Bank vice president Dario Scannapieco said that as of the end of 2017 Italy had spent just 2.5 billion of the 38 billion euros allocated to it by the EU's Regional Development Fund.