Saudi Arabia's powerful Crown Prince called the Supreme Leader of Iran "the new Hitler of the Middle East" in an interview with the New York Times published on Thursday, sharply escalating the war of words between the arch-rivals.
The Sunni Muslim kingdom of Saudi Arabia and Shi'ite Iran back rival sides in wars and political crises throughout the region.
Mohammed bin Salman, who is also Saudi defense minister in the U.S.-allied oil giant kingdom, suggested the Islamic Republic's alleged expansion under Ayatollah Ali Khamenei needed to be confronted.
"But we learned from Europe that appeasement doesn't work. We don't want the new Hitler in Iran to repeat what happened in Europe in the Middle East," the paper quoted him as saying.
Tensions soared this month when Lebanon's Saudi-allied Prime Minister Saad Hariri resigned in a television broadcast from Riyadh, citing the influence of Iran-backed Hezbollah in Lebanon and risks to his life.
Hezbollah called the move an act of war engineered by Saudi authorities, an accusation they denied.
Hariri has since suspended his resignation.