Iran's President Hassan Rouhani has pledged to wage a war aganst terrorism "to the bitter end, without equivocation"."Everyone must do their part -- to the bitter end, without equivocation," Rouhani said on Monday at a meeting with Italian President Sergio Mattarella.Earlier, Mattarella described terrorism as "one of the main threats to the international community".Rouhani is visiting Italy and France on the first trip to Europe by an Iranian leader for 16 years.Diplomacy and dialogue were the only way forward to resolving regional conflicts which impact the international order -- from Yemen to Syria and Libya, Rouhani and Mattarella agreed.Aimed at reviving trade relations and signing multi-billion dollar deals with Italian and French companies, Rouhani's visit comes after international sanctions against Iran were lifted last week following Iran's agreement to scale back its nuclear activities.During his two-day visit to Rome, Rouhani will meet Italian Prime Minister Matteo Renzi and Pope Francis together with his 120-member delegation to attend a bilateral business forum.Italy is one of Iran's top trading partners.