PRIME MINISTER Menachem Begin's talks with President Carter removed an extraneous obstacle to Middle East diplomacy and, in so doing, brought the United States and Israel closer to the hard choices remaining before both of them. It has yet to be established that this will bring the parties to a peace conference at Geneva, as Mr. Carter (without explaining how) suggested it would, or to further disengagements or other agreements leading toward an eventual settlement. But - and this isn't a minor consideration - diplomatic momentum has been sustained.

The extraneous obstacle removed was the prospect that Mr. Begin's feared personal and political inflexibility would produce an Israeli-American collision. This fear proved unfounded. By their own accounts, Mr. Begin and the President hit it off well in personal terms - although a deeper level of understanding of the division between them was suggested in their toasts Tuesday evening: Mr. Carter called for Israeli "courage" and warned that there is "no way to postpone any longer" the divisive underlying issues; Mr. Begin responded with an appeal for American "patience." In his public appearances, Mr. Begin displayed a keenness and wit and manner of reason belying his earlier images as fanatic and terrorist. The rise to power of the Begin government, it now seems plain, does not pose an insuperable obstacle to the orderly and amicable conduct of business between this country and Israel.

How productive this business will be is something else. Mr. Begin's purpose, oversold as a "secret plan," was to induce the administration to suspend its current active effort to gain Israeli and Arab assent to Mr. Carter's three basic points: the return of Israeli - occupied territory; a Palestinian homeland; and real peace, which means normalization of diplomatic, economic and cultural relations across the board. Conceivably as bait, Mr. Begin offered the hint or promise of later compromise on substance. Perhaps he simply offered an answer to the question that was bedeviling the administration as he arrived: what to do next. In any event, he asked, and apparently received, support for his preferred procedural framework: First choice is peace talks with the separate Arab states (with no PLO participation) at Geneva; second choice is separate talks outside Geneva, perhaps with Washington acting as go-between. This emphasis on procedure, we note, let Mr. Begin evade all the hard and exacerbating issues of substance. Since no route around the Palestinian impasse has been indicated, we are some what puzzled that Mr. Carter regards a Geneva conference in October as "very likely." We'll all have to wait and see.

In brief, Mr. Begin brought no miracles but he did clear the American-Israeli air. If his stress no deferring substance and getting talks going does not satisfy the administration's desire for deliberate, explicit movement toward an overall settlement, it does at least provide a framework in which Israel and one or another Arab state can take smaller steps if they choose. Mr. Begin has given Israel at least a short term tactical initiative, and he has given the United States the only opening in view to move its own longer-term policy ahead. So far, at least, no Arab has come up with a better idea.