WASHINGTON - The Pentagon announced yesterday that it will recruit as many as 1,000 foreigners living in the United States on temporary visas - including to study or work - in an unprecedented effort to fill critical shortages of medical personnel and foreign-language specialists.

The year-long experiment, approved by Secretary of Defense Robert M. Gates, was determined "vital to the national interest" at a time when the military is meeting its overall quotas but lacks sufficient numbers of doctors and nurses to treat wounded troops and needs more troops with foreign-language skills to help navigate diverse cultures.

The US military has long accepted noncitizens who are permanent residents of the United States and hold green cards. The new effort, which has been under consideration for several years, allows the Army, Navy, Marines, and Air Force to tap into the thousands of foreigners studying in the United States temporarily as legal aliens.

"The bottom line is that the Department of Defense has a critical need for qualified healthcare professionals and people with language and associated culture capabilities," said Eileen Lainez, a Pentagon spokeswoman. "Legal aliens have enriched our forces by supporting our nation in previous wars, and their unique backgrounds are especially valuable in today's global war on terror."

There are about 29,000 noncitizens serving in the military in return for expedited citizenship. Some national security leaders have been wary of opening the ranks to more foreigners, fearing what Max Boot, a senior fellow at the Council on Foreign Relations, calls a "nativist backlash."