JUST THREE WEEKS after conferring legal status on three existing but unauthorized West Bank settlements, the Israelis have planted three new ones. They have also extended administrative regulations there, which increases social benefits for West Bankers but conveys an impression of permanence. The State Department criticized both moves. It said about the new settlements that they are "unilateral illegal acts" that create "obstacles to constructive negotiations", the President evidently said the same in a message to Prime Minister Menachem Begin. The administration is right. Israel's West Bank policy increasingly mocks its insistence that all issues are negotiable. That policy impedes the negotiations President Carter seeks.

Sometimes it seem as though the Israelis are in a trance, bound on strengthening their hold on the West Bank, confirming the Arab suspicion that they are expansionists and straining their relations with the United States, no matter what. But perhaps Mr. Begin is proceeding by a calculated strategy. He may believe that if his government takes a firm line, as it has, and if he demonstrates that he has the majority of the Israeli people behind him, as he can do, that he will then be able to create a "fact" - a democratic fact, no less - that the United States will accept.

If this is so, then Mr. Begin's analysis is as faulty as his policy. We do not think this country will, any more than it should, accept such a "fact" as a West Bank that is progressively becoming Israeli territory. It is not the United States that is forcing the issue, but rather the Israelis.

The administration evidently has decided not to have an early knockdown confrontation with the Begin government on this question, or on the related question of dealing with the Palestine Liberation Organization. But we are pleased to see it's doing something better. It is continuing to reach out to the PLO, solicting its acceptance of Israel's right to exist and offering in return an open relationship with Washington and later a possible seat at the peace table. "We have no idea what they [the PLO] are going to do or when they are going to do it," a ranking State Department official said publicly the other day, "but the ball is in their court." The Israelis stick to the position that the PLO is only a terroist organization. But the U.S. is giving the PLO the chance to demonstrate that it's something more. It goes without saying, or it should, that Israel cannot be expected to deal with an organization that rejects not only its existence but also its right to exist. But if the PLO were to realized that it has before it quite literally the opportunity of a lifetime, and if it could bring itself into a true and explicit posture of moderation, then of course the Israelis would be expected to deal with it.

Some say that even if the PLO were to sign United Nations Resolutions 242 and 338 on the dotted line and add some specific assurances to Israel, the Israelis would still feel compelled to keep the West Bank. But why guess about what the answer would be? Why not keep on trying to tame the PLO and offer the choice? That seems to be Mr. Carter's tactic, and it's a good one.