Washington's single-minded pursuit of the Iran nuclear deal damaged its alliance with Saudi Arabia, experts say, and fed the escalating crisis in the Gulf.

The United States failed to manage its traditional Sunni Arab allies in the region while it reached out to mend ties with their bitter Shiite foes in Tehran.

Shaikh said he and others had warned U.S. officials "at the highest level" that its focus on Iran had hurt its traditionally warm relationship with Riyadh.

Riyadh accuses Tehran of stirring sedition among the Shiite minorities in Arab states, while Iran sees its rival as a U.S. proxy and sponsor of extremism.

Washington broke off diplomatic relations with Iran after the 1979 hostage crisis at its embassy in Tehran and has remained a close friend of Saudi Arabia.

Kerry would reject this criticism. His spokesman Kirby insisted that in pursuing a nuclear deal to make the world safer, the U.S. had not given Iran a pass.

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