ANKARA, Turkey (AP) - A senior American official said Friday that U.S. Secretary of State John Kerry will take Turkey's prime minister to task for "particularly offensive" comments he made this week equating Zionism with a crime against humanity.

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Speaking aboard Kerry's plane as he flew from Rome to Ankara, the official said the Obama administration was profoundly concerned by and disappointed in Prime Minister Recep Tayyip Erdogan's remark at a U.N. conference in Vienna.

The White House on Thursday issued a statement condemning them.

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

The official said comments like Erdogan's have a "corrosive" effect on US-Turkey relations.

Kerry opened his visit to Turkey's capital with a stop at the U.S. embassy where he paid tribute to a Turkish security guard killed in a Feb. 1 suicide attack against the compound.