US President Barack Obama planned on Monday to promote US Army General Martin Dempsey, who commanded an armored division in key battles in Iraq, to the top uniformed military position in the country, a US source said.

The source, who spoke on condition of anonymity, said Dempsey was expected to be named new chairman of the Joint Chiefs Of Staff, replacing Admiral Mike Mullen at the end of his tenure.

The White House issued an advisory saying the president, who is on his way back from Europe, would make department of defence "personnel announcements" in the White House Rose Garden.

Secretary of defence Robert Gates and national security adviser Tom Donilon will attend the ceremony, the release said.

Dempsey had been considered the most likely candidate to succeed Mullen, after Obama's "favorite general" James Cartwright was passed over amid concerns over his standing among fellow officers.

Nominating Dempsey would be an unusual move and suggested that earlier plans were scrapped, given that the four-star army general took over as chief of the US Army only in April.

Dempsey served in the Iraq war, commanding the 1st Armored Division in Iraq in 2003-04, and later led training efforts for Iraqi forces.

The search for a successor to Mullen as the president's top military adviser highlights uneasy relations between civilians in Obama's White House and top officers, who have clashed over the war in Afghanistan.

The next chairman of the Joint Chiefs will form part of a new national security team under Obama that will have to contend with the nine-year-old war in Afghanistan, turmoil in the West Asia and mounting pressure on the defence budget.

In April, Obama nominated CIA director Leon Panetta to take over as defence secretary and Afghan war commander General David Petraeus to succeed Panetta at the spy agency.

Media reports said the current chief of the air force, General Norton Schwartz, was a top contender to succeed Cartwright as the next vice chairman of the Joint Chiefs of Staff.

All the nominations must be confirmed by the Senate.

Cartwright, a technology-savvy Marine currently serving as vice chairman, has been described as the President's preferred general who drew up an alternative plan in 2009 for the war in Afghanistan, breaking ranks with senior military leaders who were pushing for a large surge of US troops.

Obama in the end agreed to most of what the military asked for, ordering 30,000 additional troops to Afghanistan. But Cartwright emerged as a favorite of a White House team that had sharply disagreed with other military leaders over Afghan strategy, including Mullen, the current chairman.

As a result of Cartwright's role in the Afghan strategy sessions and other episodes, some officers concluded he was not a "team player," raising potential questions about whether he would enjoy the confidence of senior officers, officials and analysts said.

Cartwright, known for his expertise on missile defence and cyber warfare, had once been seen as the likely successor to Mullen — whose four-year tenure ends in September. But speculation has mounted in recent weeks that he would be passed over.

Last month, the White House announced nominations for the next defence secretary and Afghan commander but not for the chairman's job.

An investigation by the Pentagon's inspector general in February cleared Cartwright of allegations that he had a sexual relationship with a junior officer.

The probe found no evidence of a romantic relationship prohibited under military rules.