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

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

Dunford, commandant of the Marine Corps, 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 the top Marine general 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.

In addition, Obama will nominate Air Force General Paul Selva, currently the commander of the U.S. Transportation Command, as 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.

Dunford, a Boston native, is a 38-year veteran of the Marines. He was commissioned as an officer in 1977 and served as a platoon and company commander for several years before moving to administrative roles.

He holds two master’s degrees and is a graduate of the elite Army Ranger School.

As the United States moved toward war with Iraq in 2003, Dunford - then a colonel - found himself in the First Marine Expeditionary Force serving as commander of Regimental Combat Team 5, the unit that would lead the U.S. invasion, seize the Rumaila oil fields and then head toward Baghdad.

Dunford’s perhaps most high-profile role was commanding international forces in Afghanistan, juggling efforts to empower Afghans and withdraw American troops despite a strained U.S. relationship with then-Afghan President Hamid Karzai.

His ability to grapple with that difficult transition made him a top contender for the post, as did his time at the helm of the Marine Corps, officials say.

Dunford’s nomination is also likely a reflection that, even as Obama prepares to leave office next year with far fewer troops at war, he will still need a chairman with battlefield experience.