Turkish Prime Minister Recep Tayyip Erdogan drew sharp criticism for comments equating Zionism to a crime against humanity at a U.N. meeting promoting dialogue between faiths, and a U.S. official said Secretary of State John Kerry will take the Turkish leader to task on Friday for the “particularly offensive” remark.

Addressing the U.N. Alliance of Civilizations conference in Vienna this week, Erdogan complained of prejudices against Muslims. He said Islamophobia should be considered a crime against humanity “just like Zionism, like anti-Semitism and like fascism.”

Israeli Prime Minister Benjamin Netanyahu sharply condemned the remark late Thursday, calling it a “dark and mendacious statement, the likes of which we thought had passed from the world.” The United States and the United Nations joined the criticism.

In Washington, U.S. National Security Council Spokesman Tommy Vietor said the characterization about Zionism, the movement to establish and maintain a Jewish state, was “offensive and wrong.”

“We encourage people of all faiths, cultures, and ideas to denounce hateful actions and to overcome the differences of our times,” he said.

Turkey and Israel were once important allies but relations have deteriorated sharply after an Israeli raid on a Gaza-bound Turkish aid ship in 2010 which killed nine pro-Palestinian activists.

Turkey is a co-sponsor, along with Spain, of the U.N initiative to promote tolerance and understanding between various religions.

A U.N. statement said: “If the comment about Zionism was interpreted correctly, then it was not only wrong but contradicts the very principles on which the Alliance of Civilizations is based.”

The statement said U.N. Secretary General Ban Ki-moon “believes it is unfortunate that such hurtful and divisive comments were uttered at a meeting being held under the theme of responsible leadership.”

Outrage over the remarks threatens to overshadow Kerry’s visit to NATO ally Turkey on his first official overseas trip as secretary of state. Kerry has spent much of his time at his first three stops focusing on the conflict in Syria.

Speaking aboard Kerry’s plane as he flew Friday from Rome to Ankara, an official said President Barack Obama’s administration was profoundly concerned by Erdogan’s words and said such comments had “corrosive effects” on Turkish-U.S. ties. The official said the comments threaten to affect not just “frozen” Turkish-Israeli relations but the whole region.

The official spoke on condition of anonymity because he was not authorized to preview Kerry’s diplomatic meetings in Ankara.

Turkey’s state-run news agency, Anadolu, reported Erdogan’s remarks on Wednesday but removed the reference to “Zionism” in a correction sent out an hour later. It said the correction was “made by the source” but gave no other explanation.

Erdogan, whose ruling party has roots in Turkey’s Islamic movement, frequently criticizes Israeli actions against Palestinians but rarely speaks out against Zionism. In November, he accused Israel of state terrorism and of an “attempt at ethnic cleansing,” a euphemism that describes using violence to force a population to flee an area.

(AP)