The US President Obama’s special advisor to the Middle East Dennis Ross resigned from his post citing family reasons.
He is the second key adviser to step down in six months, following the resignation of envoy Senator George Mitchell.
Ross had pledged to work at the White House for two years, but extended his time by another year in light of the Arab Spring upheaval.
He said he and his wife had agreed “it is time to act on my promise”.
The White House said Ross would leave his National Security Council post at the end of the year.
Dennis Ross, a seasoned negotiator and an expert in the Middle East affairs, had also served in the administration of former President Bill Clinton and has often been accused of his bias to Israel.