Thai jets and artillery pounded Vietnamese troops occupying a hill half a mile inside Thailand on Saturday, and Thai soldiers poised for an assault on the heavily mined position, military sources said.
Thai government sources in Bangkok said American-made jet fighters and heavy artillery bombed and shelled the Vietnamese before an infantry operation was to be launched in the Banthad Mountain range, 170 miles southeast of Bangkok.
Military spokesmen said the Vietnamese were dug in along the hill and had laid a string of mines to counter any Thai ground assaults.
Casualty reports from the fighting Saturday were not immediately available.
Seven Thai soldiers have been reported killed and at least 16 were injured since the fighting began. The latest reported death was on Friday, when the military said a Thai soldier stepped on a land mine while on patrol.
At least 16 Vietnamese bodies have been found inside Thailand, the Thai military said. Scores more are believed to have been wounded.
Sporadic fighting has continued along the border since late April, when 800 to 1,200 Vietnamese troops moved into Thai territory in pursuit of Cambodian guerrillas opposed to Vietnam's long occupation of their homeland.
Escalating Thai attacks have pushed some of the Vietnamese back into Cambodia, but the Hanoi government dispatched a fresh battalion of 600 to 800 men to reinforce the hilltop half a mile inside Thailand, the Thai military said.
The incursion into Thai territory has been one of the largest and longest of the Vietnamese campaign against Cambodian guerrillas.
Thailand has accused Vietnam of at least 40 cross-border forays in search of Cambodian guerrillas since last November, but the Vietnamese government has denied the charges.
Radio Hanoi on Saturday reported a Vietnamese Foreign Ministry statement denying the latest reported incursion into Thailand.
The broadcast, monitored in Bangkok, repeated Vietnam's call for a "safety zone" along the Thai-Cambodian border. The Thai government has said it cannot agree to any proposal that would require Thailand to demilitarize it territory, a move Thailand regards as infringing its sovereignty.
Vietnam has had about 160,000 troops in Cambodia for the past six years, supporting the pro-Hanoi Heng Samrin regime in Phnom Penh. An estimated 60,000 Cambodian guerrillas have been battling the Vietnamese and their Cambodian allies.
The Vietnamese recently captured the guerrillas' last major strongholds along the Thai-Cambodian border.