The EU says it is ready to study Hungary's request to be reimbursed for defending Europe's external borders against illegal immigration.
Last year, Italy replaced Greece as the main destination for Europe-bound sea migrants. About 98,000 migrants have landed on its shores since the beginning of the year.
EU member states have extended the landmark Sophia rescue operation in the central Mediterranean for another 18 months amid growing concern at the huge number of migrants crossing to Europe.
New legal action by the EU against eastern member states for refusing to take their share of refugees shows how the worst migration crisis since World War II still divides the continent.