WASHINGTON, Oct. 10 — The Marine Corps is pressing to remove its forces from Iraq and to send marines instead to Afghanistan, to take over the leading role in combat there, according to senior military and Pentagon officials.

The idea by the Marine Corps commandant would effectively leave the Iraq war in the hands of the Army while giving the Marines a prominent new role in Afghanistan, under overall NATO command.

The suggestion was raised in a session last week convened by Defense Secretary Robert M. Gates for the Joint Chiefs of Staff and regional war-fighting commanders. While still under review, its supporters, including some in the Army, argue that a realignment could allow the Army and Marines each to operate more efficiently in sustaining troop levels for two wars that have put a strain on their forces.

As described by officials who had been briefed on the closed-door discussion, the idea represents the first tangible new thinking to emerge since the White House last month endorsed a plan to begin gradual troop withdrawals from Iraq, but also signals that American forces likely will be in Iraq for years to come.