SYRIA AND ISRAEL have got themselves into a pretty fix in Lebanon. Both are guilty of the same basic offense; contempt for Lebanese sovereignty. They have assumed a right to use particular geographical areas and political groups within Lebanon for their own purposes. They have thereby made themselves hostage to an extent to the very forces they are trying to manipulate. The result is that they are, conceivably, close to war.

To pin down the start of a new phase in Lebanon is never easy, but it will do to start this one with the recent attempt of one of the Christian militias, the Phalange, to strengthen its position against the Syrians. Suspecting an Israeli plot to undermine its forward buffer position in Lebanon, Syria respondd fiercely. Suspecting a Syrian plot to undermine its forward buffer position in Lebanon, Israel responded in kind. In recent days they have abandoned some, though not all, of the longstanding tacit restrictions on the scope of their confrontation in Lebanon. Syrians have introduced helicopters; Israelis have shot some of them down. Syrians have moved up surface-to-air missiles; Israelis have uttered grave warnings in return.

Syria feels isolated and much besiged on other counts these days, and the question is whether it can find a face-saving way to back off. For Israel the question is whether it can control those of its politicians and generals who ache, in the name of protecting Lebanon's Christians, to exploit the Syrians' discomfiture. That Israel is in the middle of an election campaign doesn't help.

Everywhere -- but especially in the Middle East -- words are potential dynamite, and the United States has used some ill-chosen ones. Richard Allen of the White House staff gave the Israelis encouragement for "hot pursuit" of Palestinian border guerrillas, and they have used it as license for attacks all over Lebanon. Secretary Haig, on his recent Mideast trip, seemed to stumble briefly into what my have been a Phalange trap. He condemned the Syrians alone without apparently realizing how his condemnation would affect the situation. Now American diplomats are scrambling to cool things off.

The most interesting aspect of American diplomacy is the approach to the Soviet Union, Syria's patron and therefore a power to be reckoned with on at least the Lebanese part of the Middle East scene. Last week Secretary Haig was lambasting the Kremlin, again, as the greatest threat going to world peace, and this week he asked the Kremlin to help defuse Lebanon. So far Moscow has refused to consider a diplomatic role except to condemn Israel. It has its own interest, however, in seeing that its client does not go over the edge, perhaps dragging it along. The same goes for the United States and its client, Israel.