Vietnam said to be planning major offensive in Cambodia

Vietnam will launch a major military offensive against Cambodian guerrillas this coming dry season, well-informed sources say. The Vietnamese, who control the Cambodian government, aim to consolidate their position in that country. Vietnam will also renew efforts to open dialogue with Thailand and China, two key supporters of the Cambodian opposition, the sources say.

Like its predecessor, the next dry season offensive will be aimed at all three opposition factions -- the communist Khmer Rouge and two smaller noncommunist groups led by Prince Norodom Sihanouk and Son Sann -- and will be directed in part against guerrilla bases along the Thai-Cambodian border, the sources say. (Fighting during the last dry season, from November to April, resulted in several major incursions into Thailand and the destruction of nearly all guerrilla bases along the Thai border.)

This means there is a strong possibility that the war will spill over into Thailand again this year. A spillover may in fact happen deliberately, as Hanoi tries to put further pressure on Thailand.

A number of guerrilla bases are several miles inside Thailand, Western observers say.

The Vietnamese are reported to have recently reinforced their troops opposite one of these bases, Paet Um, a Khmer Rouge base at the far northern tip of the Thai-Cambodian border. Aid officials working on the border recently requested that a noncommunist guerrilla base near the settlement of Kap Choeng be moved farther away from a field hospital that treats Cambodian civilians.

Like previous offensives, the next Vietnamese operation will have a political as well as a military objective.

Not only will Hanoi try to do as much physical damage to coalition guerrillas (some 60,000 guerrillas in all -- two thirds of them Khmer Rouge), it will also attempt to do further damage to the morale of the opposition Coalition Government of Democratic Kam-puchea and to the confidence of its major backers. The coalition's backers are China, the US, and the Association of Southeast Asian Nations, of which Thailand is a leading member.

There are few clear signs on the ground in Cambodia of preparations for an offensive, although border watchers and aid workers say the atmosphere along the frontier is tense.

One rarely noticed but usually reliable indicator of coming combat has, however, already taken place: The Vietnamese ambassador to Bangkok, Tran Quang Co, quietly returned to Hanoi late last month for what is thought to have been a briefing on the coming offensive.

At least one other Vietnamese ambassador was probably back home at the same time -- Nguyen Trong Vinh, the envoy to Peking. Similar consultations preceded last year's unusually intense military operations. (A Vietnamese spokesman in Bangkok said that his ambassador had returned to Hanoi for ``regular consultations'' and declined further comment.)

Hanoi clearly hopes that another series of setbacks to the coalition will make the guerrillas' main supporters more disposed to discussing a political solution to the Cambodia problem.

To Hanoi, however, the core of the problem is not negotiable. Vietnam does not plan to reduce its continued control of Cambodia through the current ruling party in Phnom Penh, the Marxist Khmer People's Revolutionary Party.

Earlier this year, Hanoi and its Cambodian allies declared their willingness to allow members of the anti-Vietnamese coalition to return to Phnom Penh and play some part in political life. They added that this offer was good until 1987. At that time, the Phnom Penh government would organize elections that would signify the ``basic normalization'' of the situation in Cambodia, and there would be no more room for defectors from the coalition.

The Vietnamese have reportedly approached China secretly at least four times to suggest talks. They reportedly have been consistently rebuffed. The most recent overture was made by Hanoi on Sept. 6 and rejected five days later.

But Hanoi was reassured by China's failure to retaliate forcefully against last year's Cambodian offensive. Chinese officials had in the past threatened to respond to any major Vietnamese operations in Cambodia with military pressure along the Sino-Vietnamese border.

Last year the Chinese first threatened a ``second lesson'' -- the first was the 1979 invasion of northern Vietnam -- but then failed to follow through.

But Chinese officials later said their government had decided that their country's economic development took precedence over all other issues, including the punishment of Vietnam. Since then, the Chinese government has announced a 1 million-man reduction in their armed forces, a move that has probably further increased Vietnamese confidence.