PERHAPS NOTHING effective can be done to prevent the tragedy already staking Cambodia from claiming hundreds of thousands, if not several million more lives. Perhaps the Vietnamese, whose invasion forces are still trying to stabilize the puppet regime of Heng Samrin in Phnom Penh, would rather keep seeing the toll of famine mount than allow the international agencies to funnel relief to areas and forces controlled by China's puppet, Pol Pot. But before the West concludes in a fine fury that Hanoi's cynicism has doomed those Cambodians who survived Pol Pot, one more close look at the dilemma needs to be made.

Under the Indochina policy that took shape last year, the United States has treated the region chiefly as a field of geopolitical maneuver on the Washington-Moscow-Peking triangle. As Moscow tightened its links with Vietnam, so the administration, tightening American links with Peking, eased off its earlier quest for reconciliation with Vietnam. When Vietnam invaded Cambodia and pushed Pol Pot out of Phnom Penh, the United States became a sort of secondhand uncle to him, notwithstanding his monstrous crimes against his people. To strengthen its ties with China and to embarrass Hanoi, the administration shifed its propaganda from the crimes of Pol Pot to the illegitimacy of Heng Samrin. It has favored the seating of Pol Pot, not Heng Samrin, in international bodies. It now opposes sending food aid directly to or through Heng Samrin, on grounds that he and Hanoi will use it to feed their own soldiers and supporters, not the mass of Cambodians gnawing at roots and dying by the side of the road.

The results of this policy, in Cambodian terms, are plain. Not only has the United States forfeited an opportunity to draw Heng Samrin into humanitarian relief; it also finds itself in indirect complicity with the loathsome Pol Pot. In brief, with respect to Cambodia the pursuit of cooperation with China has left us with the worst of both worlds: scant influence, scant honor. It is not at all evident that geopolitical gains have fairly compensated.

This is not to hold the United States accountable for the starvation in Cambodia. The contending Cambodians are responsible -- and their patrons in Hanoi (and Moscow) and Peking. Domestic recriminations over the American role in the Indochina war cannot alter that. And the United States still is obliged to use what political resources it has, even including an offer to talk with Hanoi or with Heng Samrin, to bring relief to the wretched Cambodians.

It is all too likely, however, that little can be done for the Cambodians while China and Vietnam, the generators of the conflict, remain in a state of undeclared war. That is all the more reason for the United States to unhook itself from a policy that makes it a backdoor partner of Pol Pot, a proven mass butcher; it should float free. And it is all the more reason to reconsider a policy so fixed upon enhancing geopolitical accommodation with China that it makes the United States an arm of Chinese policy in Southeast Asia. If the United States cannot do much to alleviate a great tragedy, it need not remain an accessory to the fact.