Vietnamese Foreign Minister Guyen Co Thach said today that China has moved three new divisions to the Chinese Vietnamese border, either as additional pressure against Hanoi or as the prelude to a renewed round of border war.

But Thach, in an interview, expressed confidence that "we are prepared to meet any eventuality" despite the disparity in size between Vietnam, with 54 million people, and China, with a billion.

The newly arrived Chinese divisions reportedly are near Lang Son in the eastern part of the border between the two countries. The two sides were reported to have deployed nearly 250,000 men each on their heavily armed border before this development.

A Chinese division includes 10,000 to 12,000 men.

There was no indication whether the reported movement of troops was related to a warning by Peking two weeks ago that Vietnam faced "grave danger" if it continued what China and Thailand said were military raids into Thai territory. Vietnam has denied ordering its forces into Thailand.

At that time, the Chinese Foreign Ministry said China would "resolutely support" Thailand's efforts to defend its sovereignty. Thailand reported about the same time that Vietnamese troops had withdrawn from its territory, and there have been no further reports of Vietnamese raids into Thailand.

The comments by Thach today came amid reports of more frequent incidents along the Chinese-Vietnamese border and in a period of intensified military and political uncertainty in eastern Asia.

Vietnam charged China with 18 incursions or shelling incidents along their common border in June and five more incidents so far this month. A Vietnamese protest delivered to China last Friday drew a response from Peking that it was "exercising the right of self-defense," Thach said.

Thach warned Peking today that it faces the same fate as did France and the United States if it undertakes a major campaign in Vietnam.

Thach, who is Hanoi's senior diplomat, said China is by no means as strong as was the United States when it intervened in Indochina 15 years ago and he added that the Chinese people, like the Americans, can become tired of war before Vietnam will tire.

"War can bleed not only Vietnam," he said, referring to the reported Chinese aim, "but war can also bleed China."

Chinese border action seems to have increased since June 24, when a Vietnamese force reportedly crossed into Thailand, ringing alarm bells in that country and elsewhere in Southeast Asia.

As in the past, Thach today denied the Thai version of that incident and said the Vietnamese commander in the area reported his troops did not penetrate Thailand. Thach insisted that "no order" was given to Vietnamese forces to cross the border and that Vietnamese policy is "not to invade Thailand."

China, Thach maintained, is "playing the thai guerrilla card" but supporting the forces of Pol Pot, the Cambodian leader overthrown in 1979 by Vietnamese-supported troops, in efforts to set back Vietnamese military efforts in Cambodia.

"The problem of Cambodia is a problem between China, Cambodia and Vietnam but China would like to make it between Thailand, Cambodia and Vietnam," Thach contended.

Thach professed to be unimpressed with political and military responses by the United States and Thailand to the June 23 incident. He said that:

Accelerated U.S. airlifting of military supplies is "itself not a big problem" since the vast U.S. military supply buildup during the Vietnamese war "could not save the U.S. Army." More serious and harmful, he said is the "wrong" effect it may have of "encouraging the Thais."

Thailand's cutoff of rice shipments to Vietnam as a gesture of retaliation is "childish."

The latest Thai action, closing the Thai-Laotian border which is the lifeline of Vietnam-dominated Laos, "will create some difficulties but will fail."

In the first Western press interview with a Vietnamese leader since Premier Pham Van Dong and Communist Party chief Le Duan met with Soviet leaders in Moscow last week, Thach said there will be "no big change in relations between Moscow and Hanoi."

Thach characterized the meetings as "to review and strengthen relations" in the framework of the 1978 Soviet-Vietnamese treaty. Asked if there would be changes in Soviet military arrangements here, Thach said that for the foreseeable future "there will be no bases in Vietnam."

He added, "I cannot foresee the future." He said the Soviets, who reportedly are making use of Vietnamese facilities for logistical support, would be permitted to establish bases "if it were necessary for our defense and not for any other purpose."