For the first time, a United Nations Secretary General, Antonio Guterres, addressed an international gathering of Jewish leaders, pledging pledging ‘’to be on the front lines in the fight against anti-Semitism."

At the World Jewish Congress (WJC) Plenary Assembly, which opened Sunday in New York, he also stressed that “Israel needs to be treated like any other UN member state” and that it had an “undeniable right to exist and to live in peace and security with its neighbors.”

"The modern form of anti-Semitism is the denial of the existence of the State of Israel,” the UN leader added.

Guterres recalled what he called the “systematic policy of discrimination of Jews in the Middle Ages” and the expulsion of Jews from his native Portugal, which he called a “tremendous crime and the most stupid mistake ever made in Portugal.”

He also recalled his strong emotions when he visited a nearly empty synagogue of the Portuguese Jewish community in Amsterdam, because it had been decimated in the Holocaust.

Guterres said "anti-Semitism never died despite the shock of the Holocaust," and added that it was “alive and well today”, citing hate speech on the internet, physical aggression against Jews, and the destruction of Jewish monuments and cemeteries.

More than 600 Jewish community representatives from some 90 countries around the world are attending this week’s WJC’s Plenary Assembly, the supreme decision-making body of the World Jewish Congress, which was founded in Geneva in 1936.