Turkey PM's Zionism remarks attacked
He told a UN forum this week: "As with Zionism, anti-Semitism and fascism, it is inevitable that Islamophobia be considered a crime against humanity."
Israeli PM Benjamin Netanyahu strongly condemned his comments.
New US Secretary of State John Kerry is expected to raise the issue when he meets Turkey's leaders on Friday.
He is in Ankara for talks on the crisis in Syria.
But his visit has been overshadowed by Mr Erdogan's comments, made at a meeting of the UN Alliance of Civilisations Forum in Vienna earlier this week.
His words drew a sharp rebuke from Mr Netanyahu's office, which called them "a dark and mendacious statement the likes of which we thought had passed from the world".
Zionism is an ideology or movement that asserts that the Jewish people have a right to a national home or state in what was the Biblical "Land of Israel". There is no consensus among Zionists where the borders of the state should be. For Palestinians, the success of Zionism has meant the frustration of their national aspirations and life under occupation.
In the US, National Security Council spokesman Tommy Vietor said "the characterisation of Zionism as a crime against humanity... is offensive and wrong".
UN Secretary General Ban Ki-moon's office said he heard Mr Erdogan's speech through an interpreter, and called it "unfortunate that such hurtful and divisive comments were uttered at a meeting being held under the theme of responsible leadership".
Relations between Israel and Turkey have deteriorated since May 2010 when nine Turkish activists aboard a flotilla of aid ships trying to break Israel's naval blockade of Gaza were killed in clashes with Israeli troops.