"You can be assured that they will be back. The Republic of Italy has given its word in writing and we will honour that," a senior Italian government official said in New Delhiamid reports of uncertainty over their return.
Recently media reports had said the marines would not be back as they are likely to contest elections there.
Massimiliano Latorre and Salvatore Girone were allowed by the Kerala High Court this month to visit their family in Italy for Christmas.
"This (allowing them to visit Italy) is a testimony of the Indian sensitivity towards the value of the Christmas festivities considered of the utmost importance by all Italians," Italian Foreign Minister Giulio Terzi said in Italy.
The two marines were arrested from Italian vessel 'Enrica Lexie' on February 19 for shooting down two Indian fishermen off Alapuzha coast on February 15.
The Kerala High Court permitted them to go home for two weeks while asking them to give a bank guarantee of Rs 6 crore and imposing stringent conditions.
Italy has approached the Supreme Court for jurisdiction to try the marines at home, arguing the February firing took place in international waters.
Italian government sources said the issue of marines is "highly sensitive and sentimental" and they were looking forward to early settlement of case.
They said the Supreme Court here is likely to pronounce the judgement in the case in January.