Last week the Soviet Union called on the United States and Britain to resume talks on banning the underground testing of nuclear weapons. This week the Reagan administration was reported to have decided not to resume the talks on the so-called comprehensive test ban treaty. Such a decision makes it all the more important for the Senate to act on two test ban treaties that have long since been signed. Ratification could recover some of Washington's lost momentum toward controlling nuclear weapons and their proliferation.
The two unratified treaties are significant steps beyond the original limited test ban treaty of 1963, which prohibits tests of nuclear weapons in the air, underwater, and in outer space. In the threshold test ban treaty of 1974 the US and the Soviet Union agreed to limit underground testing to weapons with an explosive yield of no more than 150 kilotons ( the equivalent of 150,000 tons of TNT). In the peaceful nuclear explosion treaty of 1976 they extended the same ceiling to explosions of nuclear devices at places other than military test sites.
Though the ceiling is high (roughly 10 Hiroshima bombs), at least it moves toward the comprehensive treaty's goal of banning all nuclear tests. Moreover, by setting the same ceiling for peaceful as well as military detonations, the treaties recognize the difficulties in distinguishing between the two. And they represent negotiating breakthroughs on verification procedures. The peaceful explosion treaty includes, for the first time, provision for on-site inspections.
Last May the director of the Arms Control and Disarmament Agency, Eugene Rostow, reportedly told the Senate Foreign Relations Committee that he had run into a stone wall in trying to get an administration decision in favor of ratification. This week an agency spokesman said the status of the treaties remained unchanged.
President Reagan could reasonably ask the Senate to give its consent to these treaties while the comprehensive test ban talks remain suspended. Chairman Percy of the Foreign Relations Committee has urged administration leadership on the issue. If Mr. Reagan acts on neither the comprehensive treaty nor the existing treaties, he can hardly expect the nuclear freeze advocates at home and abroad not to notice. Nor the members and potential members of the Nuclear Nonproliferation Treaty.
The latter treaty provides countries an incentive not to develop nuclear arms by offering a commitment to limit such arms from those that already have them. The comprehensive test ban talks have been part of that commitment, symbolizing a willingness of the leaders of the nuclear club not to keep developing bigger and better nuclear arsenals while other countries refrain from building any. This total ban has been seen by many as a more persuasive gesture than the piecemeal efforts toward limiting the quantities of weapons in a continuing arms race.
A White House spokesman has described the report about not resuming the talks as ''off target.'' But ''officials'' have been cited on the reasons for a refusal to resume them.
One is supposed to be doubt about verification. But verification should be capable of negotiation as in previous treaties; or a comprehensive ban could be, as proposed, of limited three-year duration so that it could be ended if unsatisfactory; or talks could continue toward lower and lower explosion levels short of a comprehensive ban.
The perhaps more controlling reason given is an administration interest in continuing its own weapons tests during a period of military buildup. If Mr. Reagan indeed wants to preserve this option, he can do so up to a ceiling of 150 kilotons under the treaties that await ratification. Does he really want to go higher?If so, it would be well to inform the American public.