The US Army has decided to keep its elite Ranger School open to women, a high profile step in the Pentagon's efforts to remove barriers to women serving in combat.

"We must ensure that this training opportunity is available to all soldiers who are qualified and capable," Army Secretary John McHugh said.

The decision comes after a successful experiment in which two women completed the gruelling Rangers training course for the first time last month.

They showed skeptics that women can prevail in the 61-day-long test of strength and endurance, both physical and mental.

They received their coveted Ranger tabs on August 21 at Fort Benning, Georgia.

For now, women are still barred from serving in Ranger combat units, but just earning the tab is a mark of distinction that can set a young officer on a track toward top commands.

President Barack Obama's administration decided in 2013 that all combat positions should be open to women by 2016, including the infantry, artillery, armor and special forces.

The military services can request that exceptions be made, provided they are justified by operational constraints.

Defense Secretary Ashton Carter will have the last word on which positions will remain closed to women, in January 2016.

But the service chiefs appear to be leaning in favor of a total or near total opening of their forces to women, provided they meet the same physical requirements as men.

Admiral Jon Greenert, the outgoing chief of naval operations, for instance has come out in favor of allowing women into the Navy's SEALs, the elite force famous for killing Osama bin Laden.