The United States has agreed to sell Thailand advanced F16 warplanes and to speed up delivery of artillery and armored personnel carriers as the Southeast Asian nation defends its border against Vietnamese incursions, Pentagon spokesman Michael I. Burch said yesterday.

Burch said Washington and Bangkok are still working out financing arrangements for the highly sophisticated F16s, which would be the first in Southeast Asia.

"The assessment by our government and the Thai government is that they need an advanced fighter," Burch said. "We would be interested in selling them the equipment that meets their defense needs. Would we sell them F16s? Yes. Would we sell other airplanes to them if they desire them? Yes, we would consider them."

Burch declined to specify the number of F16s involved. But another Pentagon official said Congress was notified Monday of an order by Thailand for 16 of the jet fighters. Arms sales agreements require congressional approval.

Some members of Congress have opposed the sale, saying it would introduce a new level of military sophistication into an area riven by territorial and political disputes.

Thai forces have been engaged in fierce fighting this month to repulse Vietnamese troops who crossed the Thai-Cambodian border in an assault on Cambodian guerrillas. The guerrillas are trying to oust a pro-Hanoi regime in Phnom Penh.

"Certainly the instability that's been promoted by North Vietnam is a factor in all decisions regarding the security of Thailand and other friendly nations in the area," Burch said.

At Bangkok's request, according to Burch, Washington is accelerating the delivery of armored vehicles and artillery to Thailand that are stuck in the foreign military sales pipeline.

Burch said Washington gave the Thais "a balanced presentation on the capabilities and characteristics of other airplanes," including the F20 jet fighter produced by Northrop Corp. He said Bangkok prefers the F16 produced by General Dynamics Corp.