Donald Trump has raised the spectre of Iran’s nuclear programme in his first Yom HaShoah message as president.

The president was speaking from Washington to a gathering of hundreds of international Jewish leaders at the World Jewish Congress’s plenary in New York.

Only months after the White House drew criticism for failing to mention Jews or anti-Semitism in a message for International Holocaust Memorial Day, he said: “On Yom HaShoah, we look back at the darkest chapter of human history. We mourn, we remember, we pray, and we pledge: Never again. I say it, never again.

“The mind cannot fathom the pain, the horror, and the loss. Six million Jews, two-thirds of the Jews in Europe, murdered by the Nazi genocide. They were murdered by an evil that words cannot describe, and that the human heart cannot bear.”

And he stressed the importance of heed the warnings of today in memory of the victims.

He said: “We must stamp out prejudice and anti-Semitism everywhere it is found. We must defeat terrorism, and we must not ignore the threats of a regime that talks openly of Israel’s destruction. We cannot let that ever even be thought of.”

Meanwhile, Elie Wiesel was remembered as the world’s “moral conscious” during a tribute marking the first Yom HaShoah since his passing.

WJC President Ronald Lauder recalled a visit with the Holocaust survivor and Nobel laureate to Auschwitz three decades ago.

He told the gathering: Had had tremendous gifts. He could articulate complex thoughts. In a miraculous way he became the conscious of the world which was missing in the years that led to the Holocaust.”

Wiesel, he said, believed indifference in the face of the Nuremberg laws and Kristallnacht paved the way for the Shoah. “He pledged never to be indifferent to suffering. He was fearless and his courage contagious. This man gave me the courage to speak out on behalf of world Jewry. Everything I do today’s is because of the example Elle Wiesel set for the world.”

The Yom HaShoah segment saw a stirring performance from the Cornell University Chai A Capella Choir.