US Defense Secretary Ashton Carter says the American military has opened all combat roles to women in uniforms.

"As long as they qualify and meet the standards, women will now be able to contribute to our mission in ways they could not before," Carter told a Pentagon news conference on Thursday.

"They'll be allowed to drive tanks, fire mortars, and lead infantry soldiers into combat. They'll be able to serve as Army Rangers and Green Berets, Navy SEALS, Marine Corps infantry, Air Force para-jumpers and everything else that was previously open only to men," he said.

President Barack Obama called the move a "historic step forward," saying it would "make our military even stronger," according to Reuters.

"Our armed forces will draw on an even wider pool of talent. Women who can meet the high standards required will have new opportunities to serve," Obama said in a statement

Carter said the opening to women would take place following a 30-day review period, after which they would be integrated into the new roles in a "deliberate and methodical manner" as positions open. The waiting period enables Congress to review the decision and raise any objections.

He acknowledged the decision could lead to more debate over whether women would have to register for the draft- an issue he said was already under litigation.

The US military is currently an all-volunteer force, but young men are still required to register in case the draft is reactivated.

Asked whether the decision opened the door to women being required to serve in front-line combat positions, Carter said members of the military had some choices but not "absolute choice."

The decision drew a rebuke from the Republican chairmen of the armed services committees in the Senate and House of Representatives. But some other lawmakers welcomed the move.

Carter's decision comes nearly three years after the Pentagon first instructed the military to open all positions to qualified women, including front-line combat roles. A restriction on such roles was seen as increasingly out of place during a decade of war in Iraq and Afghanistan in which women were often in harm's way.

Women represented about 2 percent of US casualties in Iraq and Afghanistan, with some 300,000 deploying to the conflict zones.