U.S. President Barack Obama's key Middle East advisor Dennis Ross said Thursday, November 10, he would resign after a tenure marked by stalled US peace moves, turmoil in the Arab world and Iranian defiance, AFP reported.

The departure of Ross, a veteran peace negotiator, follows that of Obama's Middle East envoy George Mitchell in May and appears to indicate the administration has no plans for bold steps in the region before 2012 elections.

Senior officials categorically stated that Ross was not leaving because of internal tensions in Washington or over policy differences, and praised his role in deepening Iran's isolation over its nuclear program.

Ross said in a statement that he was returning to private life with "mixed feelings" but had stayed a year longer than he had intended to, during a landmark period dominated by the Arab spring uprisings.

"It has been an honor to work in the Obama administration and to serve this president, particularly during a period of unprecedented change in the broader Middle East," said Ross, who is expected to leave before the end of the year.

"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."