"It was difficult to make all the services work on it together, but we've achieved it and this is why I'm optimistic," Mesic told Radio 101 in his first interview since assuming the second term in office.
"If Gotovina is in Croatia we will certainly find him, and if he isn't, we need to get help from abroad."
Mesic said nothing was accidental in politics and journalism, and that the recent publication of details from Gotovina's criminal files was part of a specific plan, although he declined to elaborate further.
He said he found it difficult to believe that nobody in Croatia's 1990s authorities knew that Gotovina had been given three convictions in France amounting to 9.5 years in jail for robbery and kidnapping.
"Why had nobody checked his biography," Mesic wondered, saying that once, decisions in Croatia were made by former Defence Minister Gojko Susak and former President Franjo Tudjman.
Mesic said he did not approve but understood France's decision not to reveal Gotovina's convictions. Gotovina was a member of the French Foreign Legion, whose members are given French citizenship after five years of service and even bigger state benefits after 10.
Mesic feels that everyone in Croatia must "face the truth" and say that Gotovina is a fugitive from justice and has no right to protection. "He must answer before the Hague tribunal."
Asked if the authorities had a strategy in case EU entry negotiations did not start on March 17, the president said Croatia would ask for a month-long extension of the deadline to hand him over to the Hague tribunal. "If we don't start the negotiations, we won't gain access to the European Union's funds, which means that this generation will live poorly."
Commenting on Serbian President Boris Tadic's statement that it would be best if Croatia and Serbia joined the EU together, Mesic said Serbian services certainly knew the whereabouts of Ratko Mladic, Radovan Karadzic and other Hague tribunal indictees. Asked if this meant he was certain that Croatian services did not know where Gotovina was, Mesic said "somebody would have bragged".