Joseph Dunford Jr
Commandant of the Marine Corps General Joseph Dunford, Jr., testifies before a Senate Armed Services Committee on military budget matters on Capitol Hill in Washington January 28, 2015. REUTERS/GARY CAMERON

(Reuters) - President Barack Obama on Tuesday will nominate Marine Corps' Commandant Joseph Dunford as the next chairman of the Joint Chiefs of Staff, U.S. officials said on Monday, disclosing a widely expected pick likely to win swift Senate confirmation.

Dunford, 59, would replace Army General Martin Dempsey, who is expected to step down in September as the top military officer after a tumultuous four-year period that saw most U.S. forces withdraw from Afghanistan but thousands return to Iraq.

Dunford has experience in both wars and, before becoming Marine Corps commandant in late 2014, led U.S. and international forces in Afghanistan as they handed over greater responsibility

to Afghan troops battling a still-resilient Taliban.

He earned the nickname "Fighting Joe" on the battlefields of Iraq, where he helped lead forces during the U.S. invasion in 2003. He was known as a calm and thoughtful leader who created conditions for success with careful planning and harmonious execution, according to friends and colleagues.

Obama will also nominate Air Force General Paul Selva, currently the commander of the U.S. Transportation Command, as the vice chairman of the Joint Chiefs.

"A formal announcement is expected at the White House tomorrow," a U.S. defense official said, speaking on condition of anonymity.

Afghanistan Iraq Barack obama