PRIME MINISTER Begin says it's "absurd" to expect Israel to consult with the United States each time it undertakes to use its U.S.-supplied weapons in a manner that might be considered offensive. He's quite right. No sovereign state will willingly hobble its policy in that fashion. And if that is what the State Department's Robert McFarlane was asking of Mr. Begin yesterday in Jerusalem, he should have stayed home.

That is a trivial absurdity, all the same, compared with one Mr. Begin appears to be trying to foist off. The larger absurdity is his evident expectation that the United States will load Israel up with the hottest weapons going, at cut rates or for free, and then stand by humming "Hatikvah" while the Israelis use those weapons as they choose, no matter what the effects on American interests. We do not know for sure that Mr. McFarlane said something like this yesterday -- the concluding communique was uninformative -- but if he did not, he really should have stayed home.

The argument goes far beyond the formal terms or informal understanding on which weapons are provided. It goes to the essence of the American relationship with Israel. The United States has and accepts a moral obligation to support Israel's fundamental security. Mr. Begin asks it to support, in addition, an Israeli policy of force that costs the United States heavily and unnecessarily in its dealings with other countries of the region. He waves off the American contention that the diplomatic options in Iraq had not been exhausted. To win election points, he declares that the hoked up the Syrian missile crisis in Lebanon in order to distract attention from Iraq; once reelected, he resumes threatening to shoot up those missles. He greets the return of an American mediator, Philip Habib, to his Lebanese rounds with a new series of attacks on Palestininian targets. Shoot, shoot, shoot: that is the policy he asks Americans to support, to approve and to pay for.

It is wrong, however, to put all the responsibility on Mr. Begin. His reelection ends the administration's alibi for narrow-focus, crisis-centered diplomacy, and the larger responsibility now starts to shift to Ronald Reagan. So far he had concentrated overwhelmingly on shipping arms -- a flow interrupted only temporarily in Israel's case -- in the name of building an anti-Soviet consensus. The crippling flaw in this approach is that shipments and promises of arms, to Saudi Arabia no less than to Israel, have been unrelated to efforts to achieve Israeli-Palestinian coexistence. Until this central requirement is addressed, the United States will have no Mideast policy worthy of the name.