Mikhail Gorbachev's announcement that the Soviets will suspend nuclear testing for five months and continue the moratorium beyond that if the United States joins in was treated by the Reagan administration like something between a social error and an act of terrorism.

The White House responded with "swift and effective retribution." No, it said icily, a test ban was out of the question. The Soviets were totally out of line. They were engaging in a propaganda ploy, seeking to divert attention from their multiple human-rights embarrassments in Helsinki. They were mounting a sneak attack on "Star Wars," which, although it is advertised as non-nuclear, requires nuclear testing of one of its components, the X-ray laser.

Instead, the administration extended an insulting invitation for the Soviets to come to Nevada, with their instruments, to witness a U.S nuclear test. It was a way, of course, to emphasize our chronic displeasure with verification measures, which, the Reagan administration avers, permit continuous Soviet violations of treaties.

The Soviets, administration officials protested, have conducted a veritable orgy of testing and, being caught up, can rest for five months and make fools of us if we naively go along.

When Robert C. McFarlane, President Reagan's achingly earnest national security affairs adviser, was asked why the president has rejected the proposal, he responded opaquely, "Because the president wants to get serious about arms control."

Another White House operative put the politics of it more baldly: "It had to be stamped out immediately, so people wouldn't begin hoping it might happen."

McFarlane said sternly that the Soviets had agreed to a moratorium in 1958 and broke out of it when it suited their purposes. This, he said, had prompted President John F. Kennedy to reject moratoria not involving inspections.

There were, however, those who thought that Gorbachev had made an entirely appropriate gesture to observe Aug. 6, the 40th anniversary of the first atomic bomb dropped on a civilian population. In Congress, a few made wanly hopeful one-minute speeches. The Democrats, who are desperately searching for a distinguishing issue, have been scared off arms control as a party cause. Besides, in the frantic pre-recess rush, they were engaged in a bitter struggle to undo the treachery of the House conferees who had added $10 billion to the defense budget.

Midday on Tuesday, the usual suspects from the peace movement were rounded up for a news conference on Capitol Hill. They noted how easy it is to get a test ban if the political will is present. President Kennedy announced on June 10, 1963, that the United States would suspend nuclear testing in the atmosphere. Less than two months later, the Limited Test Ban Treaty was signed.

Not a word about this modest show of support for the Gorbachev test ban appeared on the evening news or in the newspapers.

Some western ambassadors expressed surprise at the administration's brusque response to the gesture. "What do you have to lose?" one asked.

From Europe, where most of the continent is out of town, the peace movement is burned out and leaders are maneuvering for places at the Star Wars trough, came a great silence.

Rep. Les AuCoin (D-Ore.), an obdurate peacenik, says he can't understand why, if we think the Soviets are bluffing, we don't call them on it.

To Paul Warnke, President Jimmy Carter's arms control negotiator, it is simple: "This administration does not want a test ban. It is not interested in arms control."

But here and there within the administration, even among the indignant thunderers, there is a ripple of unease. The proposal of a test ban, however manhandled by Reagan, could have considerable appeal in Australia, New Zealand, Japan and even West Germany.

If the Soviets hammer away at the idea at the upcoming nuclear nonproliferation treaty meeting, the summit and in Geneva, it could be revived, come fall. People may come to think that it was not just the thing for Reagan to reply to an invitation to a dove-dinner with a bid to breakfast in the desert, with bombs.

Not even the Soviets can make a nuclear test ban an inherently bad thing. A moratorium could slow down the arms race, since first-strike weapons that cannot be tested might never be built, and that could save two countries a great deal of money and the world no end of grief.