Hanoi sends chill over relations with US. Vietnam's suspension of MIA cooperation is firmly rebuffed by Congress and the Reagan administration. It also reinforces skepticism about prospects for Cambodia peace.

Vietnam has shot itself in the foot again. That's the consensus in Washington after Hanoi recently ``suspended'' cooperation with the United States - after almost a year of steady progress - in key humanitarian areas. In the move, Hanoi put the search for US servicemen still missing from the Vietnam war on hold.

Vietnam's move undercut those in Washington pushing the Reagan administration to ease up on its tough policy of diplomatic and economic isolation of Vietnam. Few observers here see much prospect for a resumption of cooperation soon.

Nor do specialists predict rapid progress on ending the Vietnamese occupation of Cambodia. Vietnam's move only reinforced suspicion that Hanoi has not yet made the tough decisions about pulling its estimated 120,000 troops out of Cambodia. Despite some hopeful signs recently, officials and congressional specialists say a Cambodian peace agreement will take time in the best of circumstances.

(Sino-Soviet talks on Cambodia, P. 7.) Vietnam reneges on joint efforts

On Aug. 3, Vietnam reversed a two-week-old decision to mount a joint effort with the US to account for US servicemen missing in action (MIA). The effort was to focus on the 70 most promising cases of the more than 1,700 MIAs lost in Vietnam. But Hanoi suspended all such cooperation, charging ``hostile'' US policies.

Vietnam also suspended talks on processing 11,000 detainees - recently released from ``re-education camps'' or prisons - and their families for possible admission to the US.

These actions snapped a year of increasing US-Vietnamese cooperation on humanitarian matters.

``This was a terrible misreading of American and congressional opinion ... a serious mistake,'' says Sen. John McCain (R) of Arizona. He had championed a bill to establish a minimal US diplomatic presence in Vietnam - known as an ``interest section'' - in the hope of increasing humanitarian cooperation. Senator McCain has suspended his initiative.

``It was a horrible and cruel thing for them to do'' to the families of MIAs, adds Rep. Chester Atkins (D) of Massachusetts.

``This did immeasurable damage'' to Vietnam, he says, but it is part of a behavior pattern that the country has followed before. He expects Vietnam will reverse itself, perhaps by fall, and progress will again be possible.

Congressional sources say the McCain initiative had majority support on the Senate Foreign Relations Committee before Hanoi's actions. Instead, the suspension brought back the bitter memories and emotions that Vietnam can still evoke. US holds firm on isolating Vietnam

Hanoi's move also reinforced administration opposition to the McCain idea. The administration argues that progress on humanitarian issues, such as MIAs, is necessary for reestablishing the full range of diplomatic relations with the US.

But the US is also participating in a boycott of diplomatic and other ties with Vietnam over Cambodia. In conjunction with the Association of Southeast Asian Nations (ASEAN) and the noncommunist resistance in Cambodia, Washington and its friends insist that Vietnam pull all its troops out of Cambodia before ending Hanoi's isolation from the noncommunist world.

This is a costly sanction for Hanoi, depriving it of badly needed trade, investment, and aid from the West. Gradually this pressure, combined with the high costs of maintaining forces in Cambodia, is pushing Hanoi to show flexibility, US officials say.

Reagan administration officials say they thought Vietnam had agreed last August to keep humanitarian issues separate from normalization of relations and Cambodia. In return for Vietnamese cooperation, the US had agreed to let private US organizations begin helping Vietnam in assisting people disabled by the war.

But Hanoi linked humanitarian and political issues early this month by refusing to help on MIAs when the administration testified against establishing a US diplomatic presence in Hanoi, pending a Vietnamese pullout from Cambodia.

On Cambodia, hope and skepticism

There have been a number of important steps forward on Cambodia that have fueled a perception of significant movement.

This summer Vietnam pledged to pull 50,000 troops out by year's end, and all remaining troops by late 1989 or early 1990 if a political solution can be worked out among the Cambodian resistance and the Vietnamese-supported government. Last month in Jakarta, Vietnam participated in a first-ever informal meeting with all the Cambodian factions and other countries in the region.

But US officials remain skeptical of Vietnam's sincerity and object to taking the pressure off now.

``We're not sure Vietnam has yet made all the hard choices,'' says a well-placed official. ``It's still trying to break out of its isolation at the lowest cost. There has been change and progress, but Hanoi is only inching in the right direction.''

US officials and congressional sources speculate that Hanoi thought it could generate more congressional pressure on the administration to bend, especially as upcoming elections could make the MIA issue even more salient. Instead it pushed the process backwards, Senator McCain says.

``We suspect Vietnam will come around, but we don't know for sure,'' says a senior official. ``Our underlying assumption remains that these humanitarian issues are of such importance to the administration and Congress that without significant progress on them, there will be no full-fledged relationship.''

``On the humanitarian side,'' he adds, ``progress can be as fast as Vietnam wants it to be. On Cambodia, too, progress could be faster,'' depending on Vietnam's choices.

The senior official says the administration will watch carefully to see if 50,000 troops really leave this year, as Vietnam has promised. He adds that even if they do go, more than that number will still remain.

While acknowledging that this may really be the beginning of a solution in Cambodia, US officials remain cautious. ``I suspect this will be an extended process,'' says one, which could stretch well into next year.

US worries about the Khmer Rouge

``There is something of a disposition [in Washington] to declare the war over and focus on dealing with the Khmer Rouge,'' says the senior official. ``But there are still 120,000 Vietnamese troops there.''

Other officials add that Thailand, a close US ally, and China will be very hesitant to move against the Khmer Rouge unless they are certain Vietnam is pulling out. Since Vietnam's invasion of Cambodia in 1978, the Khmer Rouge has been viewed by China and Thailand as the only significant lever to keep real pressure on the Vietnamese.

But as signs of progress on Cambodia accumulated this spring and summer, sentiment mounted in Washington to insure that the 35,000 to 40,000 Khmer Rouge troops operating in Cambodia would not return to power. During its 3 years in power, the Khmer Rouge was responsible for an estimated one to two million deaths. Many observers fear that as the most powerful Cambodian resistance faction, it will fill the vacuum when the Vietnamese leave and reinstitute a reign of terror.

On Aug. 8, the House of Representatives unanimously passed a resolution by Representative Atkins, which called on the US to use all appropriate means available to prevent the Khmer Rouge from regaining power.

Atkins says the US has to substantially increase its aid to the noncommunist resistance. He also hopes Washington will demand an immediate cutoff of the Khmer Rouge from China, its main arms supplier, and from Thailand, which allows the group to be resupplied through its territory. Finally, he urges steps be taken to safeguard the thousands of Khmer refugees held in Khmer Rouge-controlled camps on the Thai border.

``The administration is moving in the right direction.'' Atkins says. ``But we need more action, more quickly.''

Administration officials stress that they oppose a return by the Khmer Rouge, whom they label as brutal and depraved. ``This is the one aspect of the final settlement which the US will be particularly watchful about,'' says the senior official.

Possible next steps appear

The administration is considering new aid to the noncommunist resistance. It is also working with its ASEAN allies, a key US official says, to develop contingency plans on how to handle the Khmer Rouge, ``if and when a settlement is in place.''

US officials stress that progress on Cambodia depends on a number of actors over which Washington has limited leverage. US lobbying with China, for example, can encourage Peking to move only where it is already inclined to move.

``China's position on this has evolved considerably,'' says one well-placed official. ``We have the sense it won't stand in the way of the kind of settlement we'd like to see in Cambodia.'' But Peking needs to be convinced a Vietnamese withdrawal is near, he adds.

The next opportunity for progress on Cambodia may well be Chinese-Soviet talks on the subject set for Aug. 27. For China, a Vietnamese pullout from Cambodia is a prerequisite for normalizing ties with the Soviet Union. Moscow is eager to move in that direction and reportedly is nudging its Vietnamese allies toward a pullout.