ALTHOUGH both Vietnam and the United States have expressed the desire to put the past behind them, the war's emotional legacy continues to be the main obstacle to normalization of relations. More than four years after the last American troops left South Vietnam, negotiators on both sides are encumbered by conflicting attitudes over the charged issue of U.S. asssistance to the war-torn Vietnamese economy.

The Vietnamese government feels keenly that the United States has a moral obligation to compensate its people for the devastation and death wrought by U.S. forces during the war. The American refusal to do so is viewed by Hanor as a further expression of ill-will toward Vietnam.

The Congress, on the other hand, has gone on record as rejecting assistance of any kind, usually referred to in Congress as "reportions," a term which Hanor officials have deliberately avoided as offensive to Americans. The rejection appears to reflect the feeling that the United States has already paid enough of a price by having lost the war. One member of the House Select Committee on Missing Persons, attempting to explain to officials in Hanoi in late 1975 why the United States had not agreed to reconstruction aid, said, "America had never lost a war before, so there is still a lot of injured pride on our side."

The two rounds of talks in Paris on May 3-4 and June 2-3 were cordial enough. U.S. and Vietnamese negotiators talked frankly about the political constraints on their positions.Each side made clear it is interested in establishing a new relationship, but neither was willing to move faster toward recondition than it believes its domestic opinion will support. No date has been set for a new round, and both sides realize further talks will do little good unless there has been political shift which would permit forward movement.

Ironically, Hanoi is now calling on the administration to exert more leadership in relation to Congress in order to make a breakthrough possible on the postwar aid issue. For years, during and after the war, the Vietnamese had looked to Congress to challenge and ultimately help force changes in administration policy. During 1975 and 1976, Henry Kissinger, whose personal animosity toward his former foes appeared to shape his postwar policy, discouraged any relations with Vietnam. It was the House of Representatives which took the lead in breaking the ice, with the trips to Paris and Hanoi by the Select Committee and the passage of legislation provisionally lifting the trade embargo against Vietnam (part of a military aid bill vetoed by President Ford). Carter Cation

AS ONE of his first acts, Assistant Secretary of State Richard Holbrooke ordered a review of existing Vietnam policy. As a result, the administration has broken with Kissinger's Vietnam policy on several issues. Thus, on Jan. 24, the U.S. representative to the United Nations Development Project did not oppose a loan to Vietnam as the United States had done in the past.

The administration also rejected Kissinger's insistence on a complete Vietnamese accounting for Americans missing in action in advance of negotiations for diplomatic relations. The presidential commission led by former United Auto Workers President Leonard Woodcock went to Vietnam in mid-March with the explicit objective of removing the MIA issue as an obstacle to diplomatic relations. "The whole point of the Woodcock Commission trip was to declare that the MIAs are all dead," a State Department source said later. The Vietnamese assured the commission they would pass on MIA data as it became available, and Carter responded in a news conference, saying he thought the Vietnamese were "acting in good faith" and it was now possible to open negotiations with Hanoi.

Finally, the administration revealed during the first round of talks in Paris that it was prepared to drop the last of Kissinger's punitive policies. Holbrooke announced thath the United States would not oppose Vietnamese membership in the U.N. and offered to exchange ambassadors and then to open trade relations.

But, on the one major sticking point - the Vietnamese demand for U.S. help to "heal the wounds of war" - the administration has been unwilling to take any initiative. State Department officials, according to infored sources, made quiet efforts to persuade key congressional figures that the United States should offer some kind of postwar aid to Vietnam in connection with a negotiated agreement, but were rebuffed. Carter himself declined the oppotunity to make an appeal for public support for assistance to Vietnam. Asked at his March 24 press conference whether he felt the United States had a moeal obligation to help Vietnam, he rejected the idea as assuming the "status of culpability."

The administration put Vietnam far down on its list of priorities and decided against spending some of Carter's political capital with Congress by trying to eliminate the prohibitions on aid to Vietnam written into existing foreign aid legislation. "The President has a thousand things on his mind," one official said recently, "and he can't afford a fight with Congress on Vietnam." Inhibiting Bargaining

THE DECISION not to fight to lift the aid prohibition defined the character of the Paris talks. It meant Holbrooke could not even begin to bargain on the problem of aid. It also meant the United States would not longer be negotiating for a completion of Vietnam's accounting for the missing, over which there had been so much emotional rhetoric only a few months earlier. And the U.S. side had to ask Hanoi to back down from a demand which has become enshrined in Vietnam's foreign policy: that any new relationship must be based on U.S. help in "healing the wounds of war."

Such a retreat by Hanoi seems highly unlikely. Vietnamese leaders have a strong emotional commitment to the principle of U.S. compensation. They may also be convinced that they would pay a heavy price in loss of popular confidence in their leadership if they appeared to be abandoning that principle in reaching an agreement with the United States.

The Vietnamese will be feeling the effects of the war for a long time. Damage to the transportation system, industry and agriculture was so great that the economy is still far from being restored to its peacetime level. Massive unemployment and a serious food deficit are directly related to wartime destruction. Although hundreds of thousands of bombs and mines have deactivated since war's end, farmers are still being killed daily by unexploded ordnance. Large farming areas have been seriously affected by herbicides. Crop yields are sharply down in some areas, and Vietnamese scientists report an alarming increase in birth defects which, they believe, are linked with berbicide use. Malaria has become an epidemic problem, in part because of bomb creaters which fill up with stagnant water.

The Vietnamese have received aid from virtaully every industrialized country except the United States and from almost all multilateral agancies. But these aid projects do not meet Vietnam's overall needs. Four years ago, when Vietnamese experts in the Joint Economic Commission listed the commodities needed to rehabilitate the economy, the U.S. delegation estimated the total cost of that list at about $10 billion. More recently, Hanoi officials have emphasized to the U.S. that Vietnam is particularly in need of foodstuffs, medicines, fertilizer and building materials.

Hanoi's officials, sensitive to the political atmosphere in the United States, have sought to make an agreement on the issue of postwar aid as palatable as possible for Washington. Deputy Foreign Minister Phan Hien, chief of the delegation, had made the negotiations politically easier for the administration by telling the Woodcock Commission that the Vietnamese would not make U.S. assistance a precondition for its cooperation in providing information on America MIAs - a significant shift from previous policy.

That concession appears to have been a response to the drumfire of criticism in the U.S. press and Congress that the Vietnamese were demanding a "ransom" for MIA remains and information or were trying to "blackmail" the United States. It thus permitted Carter to negotiate on teh aid question if he wished, without submitting to any such demand.

The discussions in Paris, as reconstructed on the basis of interviews with officials on both sides, including Phan Hien, centered on explanations by each side as to why its position could not be changed and arguments as to why the other side would have to change its position. Holbrooke, citing the legislative prohibition on aid, told his conterpart that the only agreement possible was an immediate exchange of embassies to be followed by establisment of trade relations. Failure to accept this offer, Holbrooke reportedly said, could mean a much longer wait for diplomatic relations. He pointed out that it took 13 years to establish diplomatic relations with the Soviet Union and 23 years to establish a liaison mission with China. "Do you want to wait 23 years before we have realtions?" Holbrooke is said to have asked.

Phan Hien, for his part, told Holbrooke that it was impossible for his government to accept the U.S. proposal, because "if the U.S. sets up an embassy and rises the U.S. flag and U.S. officials come to Hanor, but the U.S. hasn't helped on healing the wounds, the Hanoi people wouldn't understand at all." If the Carter administration wants to have normal relations, he said, it must "have imagination" in order to persuade Congress to lift the restrictions on aid.

Vietnam's chief delegate offered an alternative to the Holbrooke plan: a "package deal" which would cover not only diplomatic relations but the postwar aid and MIA accounting problems as well. The Vietnamese-proposal, according to informed sources, did not demand that the United States fulfill its postwar aid obligation in advance of diplomatic relations. It only called on the U.S. to start the process of helping Vietnam "heal the wounds of war," leaving the form of that help to be negotiated. The clear implication of the Vietnamese proposal was the Hanoi no longer expects a substantial rehabitation aid program to be passed by Congress before relations with Vietnam warm up.

Phan Hien also pressed Holbrooke for a private pledge to support a particular level of assistance after diplomatic relations were established, even though that couldn't be written into an agreement. Such a pledge was impossible, Holbrooke said, pointing to the reaction in Congress against Nixon's secret agreement on postwar aid to North Vietnam in connection with the 1973 Paris Agreement. Holbrooke added he had to work closely with Congress on such matters and could not withhold any information. Phan Hien said he understood that, but still sought some assurance that the administration would negotiate an aid agreeement after normalization of relations.

Holbrooke agreed to study the Vietnamese "package deal" proposal back in Washington, but, according to informed sources, it was not given serious consideration. The administration's reluctance to negotiate on anything but exchange of embassies was strengthened by House passage of two amendments introduced by conservative Rep. John Ashbrook (R-Ohio) during the week following the first round of talks. The first amendment aimed at prohibiting any negotiations on aid to Vietnam, while the second opposed trade with Vietnam. Neither of them had any practical effect, but they expressed a petulant congressional mood toward Vietnam. The result was that the State Department retreated further from negotiations on "healing the wounds of war," rejecting even those moves which might have been made without prior congressional approval, such as voting in favor of loans to Vietnam in the international lending institutions rather than merely abstaining.

The second round of talks thus produced no movement in the position of either side. The Vietnamese sought to demonstrate a cooperative attitude on the MIA question by giving the U.S. delegation a new list of 20 more soldiers whose bodies they had identified. But the U.S. side reitered its inability to negotiate on anything but diplomatic relations. "This time we can't do anthing more," Holbrooke declared. Phan Hien expressed disappointment, calling the U.S. rejection of negotiations over postwar aid "a cold shower to Vietnamese public opinion." Mutual Suspicions

AFTER TWO rounds of talks, each side still seems to fear that the other is trying to manipulate it. According to informed sources, Holbrooke feels the Vietnamese have a no real problem with their own people that could not be changed by Hanoi's use of the comminications media to persuade the public. Phan Hien believes the administration is not doing what it could do to change the views of Congress. Holbrooke feels that the Vietnamese regard normalization of relations as something the U.S. wants and is therefore willing to pay a price to obtain, while Holbrooke views it as equally valuable to both sides. The Vietnamese, for their part, suspect that the United States still believes Hanoi needs normalization of relations more than Washington does. They make it clear that, while they want diplomatic and economic relations, they don't want them badly enough to yield on what they consider a basic principle.

Each side now views the future prospects for an agreement in a characteristic manner - the Americans with pessimism, the Vietnamese with optimism. Holbrooke's view, according to informed sources, is that the longer the deadlock lasts, the more difficult it will be to unfreeze the conflicting positions and normalize relations. The Vietnamese, while recognizing that there are "rough times" ahead in U.S.-Vietnam relations, say they believe Americans will eventually understand their position, if given a chance.

Sooner or later, there will be an accommodation on the one remaining issue keeping the two government's apart. But it probably won't come until the American political system can deal with its past role in Vietnam with more detachment than at present - or until President Carter gives U.S.-Vietnam relations suffient importance in his foreign policy opinion. For the greatest irony of the present situation is that, after the longest and costliest war in American history, relations with Vietnam are now relegated to such an obscure place in American foreign policy.