IN THE NAME of pacifying a border zone, the Israeli army is ranging far beyond that zone to destroy all the PLO forces and infrastructure it can. There is a logic to this policy for Israel, since the decimation of the PLO would keep it, for a time, from setting up again on the border. But it is an Israeli logic, not an American logic. The American interest is not to destroy the PLO, but rather to induce it to accept Israel, and vice versa. The United States supports Israel's legitimate efforts to brace itself against terror, but it cannot condone a sweep that is laying waste to a good fraction of Lebanon and its people. Certainly the United States does not wish Syria to be drawn into the war, as it yet could be, given the Israeli thrust.

As Israel's military plans become clearer, so do its political purposes. The Begin government may intend to secure the territory with its own forces until others, especially the United States, can be induced to share the burden. But the notion that Americans should take part in, or take over, an occupation of an Arab country with which Israel is in a state of war is a nonstarter. If the Israelis have gone into Lebanon in the hope that Washington will pull their chestnuts out of the fire, or in the hope that circumstances will leave Washington no alternative, illusion and deception have replaced the sense of reality and trust that ought to be guiding U.S.-Israeli relations.

In a difficult place and at a difficult time, the Reagan administration has been more than understanding of the accumulation of events and pressures that led Israel to move into Lebanon. At no small cost to its standing elsewhere, it has linked and given equal billing to the requirement for Israeli withdrawal and the requirement for Palestinian border restraint. This measure of principled support can be sustained, however, only if it is balanced by Israel's acceptance of goals and tactics that are consistent with broad American interests. The war must be quickly checked and a fair chance given, if it is at all possible, to a new, peaceful arrangement of Lebanese political forces.

The danger right now is that Israel, either in cold calculation or in the heat of battle, is going too far. That would leave the United States no choice but to set aside the Palestinian provocation and to concentrate simply on getting Israel's forces back behind its borders.