Secretary of Defense Caspar W. Weinberger, midway through his four-day visit to South Korea, today got a glimpse of the first detachment of U.S. Air Force A10 anti-tank jets to be based in Asia.

Weinberger was here to dedicate a $33-million facility built and paid for by the Koreans to house American pilots and ground crews for the twin-engine planes, which are billed as probably the most lethal tank-destroyers in the world.

Eight A10s joined South Korea's arsenal earlier this month at the air base here, about 50 miles south of the Demilitarized Zone marking the border with the Communist North. Another six are scheduled to arrive next month, with a full 24-plane squadron expected to be operational in a year. Officials here said there are tentative plans to double that number eventually.

Of the estimated 452 A10s, most of which are scattered among Air Force units in the United States and Europe, the ones stationed in South Korea could prove the most crucial in an actual battle, according to pilots and planners here.

This is because the principal strength of the North Korean Army lies in its force of about 2,600 tanks. Most of them are older Soviet-built T54 models but some later model T62s now are being produced in North Korea.

The A10, which is built by Fairchild Industries in Maryland and New York, has the ability to fly low and slow and maneuver close to the ground. Designed specifically to destroy tanks, the plane carries a variety of bombs and rockets but its main weapon is a 30mm rapid-fire cannon that sprays 4,000 rounds a minute of armor-piercing ammunition.

Lt. Col. Eben Jones, an A10 pilot here, says the plane's maneuverability, combined with Korea's mountainous terrain and the short flight-time to any would-be battlefield, makes the plane an ideal weapon.

"These A10s augment considerably our capability to meet and defeat the North Korean armed forces, most especially their armored forces, should Kim Il Sung, the North Korean leader, be rash enough to attack," Weinberger said.

Earlier in the day, Weinberger and South Korean Defense Minister Choo Young Bock attended the 14th annual U.S.-Republic of Korea security consultative conference.

Choo publicly called for the United States to offer improved terms for military credits and permit South Korea to sell arms to other countries.