By David Alexander

WASHINGTON (Reuters) - The Pentagon is preparing to open thousands of military jobs including medics and intelligence officers to women in the U.S. Army and Marine Corps, a move likely to shift them closer to the fighting and rekindle the debate on women in combat.

Under new rules set to be unveiled on Thursday, the Defense Department would continue to prohibit women from serving in infantry, armor and special operations units whose main function is to engage in front-line combat, defense officials said.

The new policy would open about 14,000 jobs to women by enabling them to take positions such as medics, intelligence officers, radio operators and military police at the battalion level, which had previously been considered too close to combat, officials said.

There has been significant resistance in the United States to women serving in combat. Current Pentagon rules attempt to shield women from combat, but the distinction is often lost in a war zone. Officials said 144 women in the U.S. military have been killed in the wars in Iraq and Afghanistan and 865 wounded.

Nearly 12 percent of U.S. forces deployed to Iraq and Afghanistan were women. They represented about 2 percent of U.S. military deaths in those wars.

"We believe it's very important to explore ways to offer more opportunities to women in the military," Pentagon Press Secretary George Little said. "It doesn't stop today. We'll continue to look for ways to open more positions to women in the military."

Under a policy adopted in 1994, women are allowed to serve in combat units as medics, intelligence officers and other jobs at the brigade level, which is a force of around 3,500 people.

But a woman could not be assigned to perform the same job in a battalion, which can be as small as a few hundred troops and whose forces are more likely to be directly exposed to combat.

The military has sometimes gotten around the rules by attaching women to battalions, which allowed them to work in the smaller units but kept them from officially receiving credit for being in combat.

Since combat experience is a factor in promotions and job advancement in the military, women have had greater difficulty than men in moving up to the top ranks, officials said.

The Pentagon's plan to change its rules now goes to Congress, which has a period of time to review the policy shift before it goes into effect, probably sometime this summer. During that period, Congress potentially could take action to oppose the policy changes.

(Editing by Will Dunham)