(ANSA) - BELGRADE, JUN 12 - Serbian President Aleksandar Vucic, who attended the fourth Ukraine-Southeast Europe summit in Odessa with Ukrainian leader Volodymyr Zelensky, was the only leader who did not sign the final declaration, which called for tighter sanctions against Russia. "The declaration was a document that was not simple and easy for us, and that is why I abstained, with my name and that of Serbia not appearing among the signatures," Vucic said after the meeting, according to Belgrade media. (ANSA).