Dennis Ross has decided to step down from his post

Dennis Ross, a senior aide to US President Barack Obama on the Middle East, has decided to step down from his post, the White House said on Thursday.

It was not immediately clear who would replace him.

 “Dennis Ross has an extraordinary record of public service and has been a critical member of the president’s team for nearly three years,” White House press secretary Jay Carney said in a statement.

Ross, a special assistant to the president, had initially pledged to work for Obama for two years, but extended his time at the White House by another year in light of the Arab Spring upheaval reshaping the region, Carney said.

His departure casts additional doubt over Obama’s Middle East strategy, and follows the resignation in May of Middle East peace envoy George Mitchell.

Ross, who turns 63 in two weeks, dealt a blow last month when the Palestinians gained membership of the UN cultural agency UNESCO, something Obama had sought to prevent.