WASHINGTON - US President Barack Obama called Saudi King Adbullah on Thursday to offer condolences on the death of Crown Prince Nayef and welcomed the appointment of Prince Salman as next in line to the throne, the White House said.

It was Obama's second phone conversation in less than a week with the ruler of the world's largest oil exporter. They spoke last Thursday amid concerns about escalating violence in Syria and plans to widen sanctions on Iran.

"The president expressed his appreciation for Crown Prince Nayef's many contributions over decades of service, particularly his leadership in building the strong counterterrorism cooperation," the White House said in a statement during the official mourning period.

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