WASHINGTON: US President Barack Obama's top spokesman Robert Gibbs said Wednesday he will step down and work outside the White House as an advocate for his boss, as an administration reshuffle gathered pace.

Gibbs, one of Obama's closest advisors, possesses sharp political instincts and a sometimes tart briefing style. He plays a central role in the White House and is not limited to the traditional press secretary portfolio.

He told AFP he would work on Obama's 2012 reelection bid, continue to advise his boss from outside the White House and take to the speaking circuit in support of the president and his policies.

The departure of Gibbs, who was to conduct his first briefing of 2011 later on Wednesday, comes as Obama contemplates a reshuffle to freshen his administration and as his reelection campaign machinery begins to stir.

“For the last six years, Robert has been a close friend, one of my closest advisers and an effective advocate from the podium for what this administration has been doing to move America forward,” Obama said in a statement.

“I think it's natural for him to want to step back, reflect and retool. That brings up some challenges and opportunities for the White House, but it doesn't change the important role that Robert will continue to play on our team.”

The brutal hours and high pressures of working in the White House exact a heavy toll on staffers, and it is not unusual for press secretaries and other senior advisors to have a limited shelf life.

Obama is also seeking to refresh his brain trust following the Democratic wipeout in mid-term elections last year and as Republicans challenge the administration with their takeover of the House of Representatives.

The president has been considering naming William Daley, a former Clinton-era commerce secretary who has ties to the business community, as his White House chief of staff, following the departure of Rahm Emanuel last year.