One of U.S. President Barack Obama's top Middle East advisers is stepping down from his post.

In a statement Thursday, White House Middle East Envoy Dennis Ross noted that his term has covered, what he called, “a period of unprecedented change” in the Middle East. But he said he had promised his wife he would serve only two years, and it was time to keep that promise.

White House spokesman Jay Carney said President Obama appreciates the fact that Ross extended his stay by nearly a year to deal with the rapidly changing political atmosphere in the Middle East that has been dubbed the “Arab Spring.”