U.S. stealth fighter jets and other warplanes brought to South Korea for joint war games will remain to act as a deterrent against North Korea, the U.S. military said today. The planes are the newest part of an increase of U.S. military force in the region during heightened tensions with the communist North over its nuclear program.

A statement from the U.S. military said that an unspecified number of radar-evading F-117s, some F-15E Strike Eagle fighters and a small Army task force that were brought to South Korea for exercises with the South Korean military will stay in the country.

More than 85 percent of the forces deployed to South Korea for the exercise will leave, the statement said. They include the aircraft carrier USS Carl Vinson and thousands of soldiers, Marines, sailors and Air Force personnel.

A spokesman for South Korea's Unification Ministry said retaining the stealth aircraft would send a message to the North Korean capital, Pyongyang, that it must not threaten its neighbors while U.S. forces are focused on Iraq.

But some analysts said that North Korea might see the planes as a significant threat. The F-117s would be capable of attacking a broad variety of targets in North Korea, including the Yongbyon nuclear plant. North Korea has accused Washington of plotting an attack on the facility.

Earlier this year, the U.S. Air Force moved B-52 and B-1 bombers to the Pacific island of Guam to be closer to Korea. Other specialized aircraft have also been deployed to bases nearer the Korean Peninsula.

The last time the United States based stealth fighters in South Korea indefinitely was in 1994 when Washington was embroiled in a similar dispute with North Korea about its nuclear program. President Bill Clinton considered a surgical strike on Yongbyon, but the crisis ended peacefully.