Rome had called for Brussels to take over full responsibility for the problem after hundreds of migrants have died this year attempting the treacherous crossing from north Africa.
Italy said in August it could not afford to continue its "Mare Nostrum" operation, launched after two deadly shipwrecks in October 2013.
It called for the EU border agency Frontex to assume control of the operation, which costs €9 million ($11 million) per month.
EU Home Affairs Commissioner Cecilia Malmstroem said the bloc will send two planes and three patrol vessels as part of its new "Triton" mission, but only to support rather than replace Italy's efforts.
Brussels has issued appeals to the EU's 28 member states to provide the planes and boats, as well as cover the monthly budget of €2.9 million.
"It is clear that the Triton operation cannot and will not replace Mare Nostrum," Malmstroem said.
"I am confident that Italy will continue to fulfill its European and international obligations and the European Commission stands ready to continue providing European assistance to such initiatives."
The EU's Triton mission would cover 30 miles (48 kilometres) off the Italian coast, which includes 18 miles of international waters and the area around the Italian island of Lampedusa, where many tragedies have occurred.
Italy's Mare Nostrum covers a broader area right up to Libyan territorial waters. Libya is the main launch site for migrants crossing the Mediterranean.
Two Italian vessels will also take part in Triton, named after a mythological Greek sea god, but with EU financing.
An EU source said Frontex will also send seven teams of guest officers to screen, debrief and identify migrants, mainly in Sicily.
"It's not just a wish. We're aiming at starting the operation at the beginning of November," the source said on the condition of anonymity.
However, an increase in the Frontex budget for 2015 has yet to be agreed by the European Parliament and member states.