SURPRISE: Leonid Brezhnev objects to the Reagan START proposals. Mr. Reagan, he complains, would bite into the branch of strategic arms, land-based missiles, in which the Soviets have made their heaviest investment. Mr. Brezhnev offers another approach, centering on freezing deployment of the new weapons with which the Reagan administration intends to reduce what it (alone) regards as the current Soviet edge.

The Brezhnev approach, in its current form, is no more acceptable to the administration than its proposals are to the Kremlin. Mr. Brezhnev invites the United States to surrender, by a freeze, its arms- building leverage in the negotiations about to begin. He skips past Mr. Reagan's concern for those especially accurate and powerful, and therefore dangerous and destabilizing, land-based missiles.

The Kremlin is operating on its old SALT I and II premises--that rough parity exists and that it will be accepted as such by both powers. It can see the nuclear debate bubbling in this country as in Europe, and it wishes to put Mr. Reagan's arms- building and arms control programs to the test of public opinion over the next year or two. For his part, Mr. Reagan has repudiated the earlier SALT premises, and he appears confident his strategic and political logic will carry him through. 4 That the first strategic arms talks in three years are about to begin is no small comfort to those of us who feel that a negotiating connection is a vital American interest, the more so that political tensions are bound to roil Soviet-American relations indefinitely. But to look at the divide separating the opening bargaining positions, and to think of the conviction and bureaucratic weight behind them, is to realize that what Mr. Reagan and Mr. Brezhnev are now joining is a negotiation that may go on for years--conceivably until long after both men have departed from power. In the interim, is arms building to run free?

Its superior economic and technological base gives the United States an advantage, or at least a temptation. But the Soviet Union has a countering advantage: its relative immunity to public opinion. A realistic observer might find a wash.

To stay in the game for the long haul, Mr. Reagan must stay in it for the short haul. The best way is to go back to SALT II and, if not to ratify that treaty, to use and update its valuable provisions. Mr. Brezhnev is ready to "preserve everything positive that has been achieved earlier." It would cost Mr. Reagan nothing except a bit of pride, and it could bring the country benefit, to agree.