Dennis Ross, a senior aide to President Barack Obama on the Middle East, has decided to step down from his post, the White House said on Thursday, in a further setback to the president's Middle East peace strategy.

"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 Middle East, 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 had been central to Obama's efforts to revive peace talks between Israel and the Palestinians, dealt a blow last month when the Palestinians gained membership of the UN
cultural agency Unesco, something Obama had sought to prevent    

The US and Israel believe the Palestinians should try to establish a state through direct peace talks, which broke down nearly a year ago, and they say that action at the UN will make it harder to resume negotiations.

"Obviously, there is still work to do but I promised my wife I would return to government for only two years and we both agreed it is time to act on my promise," Ross said in a brief resignation statement. - Reuters