Italy has threatened to stop vessels of other countries from disembarking migrants at its ports.
It comes as Italy’s representative to the EU, Maurizio Massari, warned in a letter to the bloc the situation had become “unsustainable”.
Prime Minister Paolo Gentiloni has accused other European nations of “looking the other way”.
More than 73,000 migrants have landed in Italy this year, an increase of 14% on the same period last year.
Some 2,000 have died or are missing feared drowned, the UN’s refugee agency says, the vast majority attempting the crossing from Libya.
Libya is a gateway to Europe for migrants from across sub-Saharan Africa and also from the Arabian peninsula, Egypt, Syria and Bangladesh. Many are fleeing war, poverty or persecution.
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The Italian coastguard takes the lead in co-ordinating rescue operations, but many of the vessels sail under the flags of other nations, many of them based in the EU.
An Italian government source told Reuters: “The idea of blocking humanitarian ships flying foreign flags from returning to Italian ports has been discussed.
“Italy has reached saturation point.”
However, it remains unclear whether it would be legal to block rescue ships.
Italy’s threat came as Mr Massari met European Commissioner for Immigration Dimitri Avramopoulos to discuss the crisis.
It also follows a poor showing by the centre-right Democratic Party in local elections at the weekend, losing out to the anti-immigration messages of Forza Italia and the Northern League.
Italy has seen more than 500,000 migrants arrive by boat since 2014.
The closure of a land route north through the Balkans has added to the pressure.
A note on terminology: The BBC uses the term migrant to refer to all people on the move who have yet to complete the legal process of claiming asylum. This group includes people fleeing war-torn countries such as Syria, who are likely to be granted refugee status, as well as people who are seeking jobs and better lives, who governments are likely to rule are economic migrants.