"I express my closeness to Salvatore Girone and Massimiliano Latorre and I confirm the commitment to resolving a dispute that has dragged on for too long," Mattarella was quoted as saying by the Italian ANSA news agency.
The two marines Latorre and Girone on board ship 'Enrica Lexie' are accused of killing two Indian fishermen in 2012 off the Kerala coast after mistaking them for pirates.
While Latorre is in Italy on medical grounds since September 2014, Italy has been seeking Girone's return as well.
However, Italy has repeatedly contested India's jurisdiction amid long delays and last year it took the case to an international court of arbitration in The Hague.
Last month, at the 13th India-EU Summit in Brussels, the two sides failed arrive at any understanding on the dispute as they stuck to their respective position and expressed their confidence in the arbitration procedure on the case currently underway in the framework of the United Nations Convention on the Law of the Sea (UNCLOS), to which India and Italy are strongly committed.