THE NEW SINO-SOVIET border incident, the first one published in nine years, appears to have been small, not to say curious. A Soviet patrol, pursuing, Moscow says with a straight face, an "armed criminal," pushed a few miles into Chinese territory and evidently roughed up some Chinese. Peking denounced the incursion as "serious" and "grave." But border talks, suspended for 14 months, were at once conspicuously resumed.

Given the continuing bad blood between the two Communist giants and their importance in the whole geopolitical scheme, the most trivial incident along the world's most hostile and heavily armed border is politically riveting. Was the Soviet crossing a local accident, an operation staged to focus Peking's attention on the border talks, a calculated act of general intimidation? Was Peking's bristling response itself a provocation an action to focus Moscow's attention on the border talks, a reminder to the United States - on the eve of White House adviser Zbigniew Brzezinski's trip to Peking - that the Soviet Union is too treacherous to engage in detente?

For the moment, we'll pass. We note, though, the central issue raised. Americans have an immense interest in seeing the Soviet Union and China remain rivals of each other, rather than partners in a common rivalry against the United States. Even with its antagonism for China, the Soviet Union in particular has plenty of distrust left for the United States; China has considerably less. But without their mutual antagonism, both Communist powers might become substantially more troublesome to Washington and less inclined to cooperate across the board. It was precisely to give China a stake in a relationship with the United States, and thereby to give the Soviet Union pause, that Richard Nixon went to Peking.

Mao Tse-tung's personal hatred of Soviet ideology alone ensured Sino-Soviet hostility; there were, of course, many other factors. His death in September 1976 and his successor's change of emphasis from internal revolution to industrial modernization raised sharply the question of whether a certain reconciliation might follow. It hasn't yet, but who's to say it won't? The border incident suggests one possibility, the quick patchup another.

Given the uncertainty, many Americans have wondered if the United States should cement its relationship with Peking before China is "lost" again. In this spirit, the movement for "normalization," by ending diplomatic and defense ties to Taiwan, has been pressed. But neither conservatives eager to keep Peking in the line against Moscow nor liberals anxious for normalization for its own sake have found generally acceptable the act and symbolism of backing off from Taiwan. This has led American policy to seek ways short of normalization to show respect and friendship for China - the Brzezinski visit, for example. Policymakers realize, too, that China appreciates every American show of strength and will, even as it laments what it regards as regular American shortfalls in the strength and will department.

The best American policy is to strengthen the Moscow connection and the Peking connection. This was the Nixon-Kissinger-Ford policy, and it is essentially the Carter policy. Trouble on the Sino-Soviet border merely underscores the American need to pursue deeper relations on both sides.