There is very little to commend Vietnam's communist rulers. They are aggressive, xenophobic and inflexible, and their record on human rights as demonstrated in their brutal expulsion of unwanted people is dismal.

But with all this, it seems to me that the Carter administration ought to reopen negotiations aimed at establishing formal diplomatic relations with the Hanoi regime -- for reasons that essentially serve American interests.

In other words, I submit, nothing is to be gained by rejecting the Vietnamese, however despicable they may be. On the other hand, a good deal may be gained by extending them recognition.

For one thing, a matter of principle is involved. Diplomatic ties do not signify approval, but simply imply recognition that a government controls its own territory.

So it is pointless to ostracize Vietnam when America maintains links with equally unsavory regimes in Asia, Africa and Latin America. Positive strategic considerations, moreover, add weight to the argument in favor of reaching some kind of accommodation with Hanoi.

Over the past year, Vietnam has slid deeper and deeper into the Soviet camp -- so much so that it has become almost entirely dependent on the Kremlin for economic and military aid. This reliance on Moscow has antagonized China, which perceived Vietnam to be a Soviet base.

The available evidence indicates, though, that elements within the Hanoi hierarchy would like to dilute Vietnam's dependence on the Russians.

Despite pressure, for instance, the Vietnamese continue to deny to the Soviet Union any permanent use of the former U.S. naval facilities at Da Nang and Cam Ranh Bay. Soviet transport aircraft shuttle around Indochina, but only to move troops and supplies for the Vietnamese.

This suggests that an American presence in Hanoi might provide the Vietnamese with an opportunity to shift away from their close ties with the Soviet Union, which would benefit both the United States and China.

Another factor in the equation is the future of Cambodia, which has become a Vietnamese satellite. Tensions in the area are unlikely to abate until Cambodia's real independence is restored, perhaps under its former leader, Prince Norodom Siahanouk.

But the chances of a Cambodian compromise being achieved under present conditions are remote. Here again, a full-time American mission in Hanoi might be an advantage in getting talks of some sort started.

It is plain, meanwhile, that the Vietnamese leadership itself has been split over how to proceed toward the United States. According to specialists here, Premier Pham Van Dong and Foreign Minister Nguyen Co Thach have been pushing for a deal with the Carter administration, while the Communist Party boss, Le Duan, has opposed any change in position.

In an apparent effort to embarrass his internal rivals, Thach claimed last month that negotiations with the United States had been going on since June. The State Department denied his assertion, but his statement nevertheless reflected a desire to see talks resume.

Actually, the Vietnamese themselves muffed the chance for relations with the United States at the beginning of the Carter administration by demanding that America award them some $3 billion in war reparations.

That demand stiffened resistance in Congress, which not only resolved that Vietnam receive no reparations, but also barred U.S. funds from going to Hanoi through international organizations.

The Vietnamese retreated from that demand by the summer of last year, but it was too late by then to get the process regenerated.

The Carter administration was edging toward normalization of relations with China at the time, and the president could not plausibly court additional political risks at home by pursuing the Vietnam card as well.

Besides, the Vietnamese damaged their own cause by invading Cambodia and by hounding thousands of ethnic Chinese as well as their own citizens to flee Vietnam, thereby creating the refugee crisis that still blights their reputation.

Within recent weeks, however, the Vietnamese have been striving to look respectable. They have pledged to make the refugee exodus more "orderly," and they have hinted at the possibility of a compromise on the Cambodia question.

In my estimation, therefore, they are signaling to the Carter administration that they want to return to the conference table -- and their signal is worth a response.

The domestic political costs to the president of such a gesture would be minimal, since his principal foes, Edward Kennedy and Jerry Brown, hardly would challenge him on this issue.

Thus, the administration has room for maneuver on the question, and it can initiate steps that in the end would contribute to the stability of East Asia.