Mesic said in a note he was saddened by Rau's death, adding that the former president and Social Democrat would be remembered by his statement that he wanted to be the president of all German citizens, not only those holding a German passport.
The Croatian president said he had the fortune to meet Rau on a number of occasions, describing him as a wise statesman with a keen interest in world events and a sincere advocate of European unification.
Mesic asked Koehler to convey his condolences to Rau's family.
The 75-year-old Rau died today after a long and grave illness, his family in Berlin said.