More senior White House staff are to leave in the next few months, adding to the high exit rate from President Barack Obama's administration.

Political analysts attribute the attrition rate to exhaustion, but Republican opponents blame disarray inside the White House, with an insular team responsible for too many policy failures.

The imminent departures include those of defence secretary Robert Gates, who has said he hopes to retire early next year, and Obama's senior White House adviser, David Axelrod, who is planning a return to his home town of Chicago early next year to concentrate on planning for Obama's 2012 re-election bid.