WHEN Mikhail Gorbachev became leader of the Soviet Union, it was said that behind his smile were ``teeth of iron.'' In the past few days, he has sunk those iron teeth into American foreign policy, biting off a sizable chunk of the Reagan administration's credibility.
In the first real test of strength on the way to the summit, the score looks like Gorbachev, 1; Reagan, 0.
Though the Daniloff case is still to be resolved, so far the White House looks defensive and outmaneuvered by the Soviets.
Consider what the Soviets have so far achieved:
1. They have committed what the Reagan administration, confronting a lesser power, would call an act of state-sponsored terrorism by seizing and holding hostage an innocent American citizen. So far, they are getting away with it.
2. Despite all the huffing-and-puffing denials from the White House, the Soviets have forced the United States to concede initial equivalency between the presumably innocent Nicholas Daniloff and Gennady Zakharov, the Soviet official the Federal Bureau of Investigation believes it caught red-handed in New York in the act of espionage.
3. Soviet success to date may embolden the KGB security bureau to try the formula again: If you want to spring a Soviet spy caught by the Americans, nab an American as hostage for exchange.
4. By rejecting President Reagan's personal pledge that Mr. Daniloff is not a spy and bringing espionage charges against the American correspondent, Moscow has told the world it thinks the President of the United States is a liar.
5. As a side bonus, the Soviets have probably dampened the vigor of the foreign press corps in Moscow. Valiant reporters though they may be, which of them is ready right now to pick up a packet of provincial press clippings, or ask questions about Soviet troop movements in Afghanistan?
The last chapter is not yet written, of course, in the story of Daniloff, the U.S. News & World Report correspondent in Moscow. But by trading, at least initially, equal treatment for Mr. Zakharov to that afforded Daniloff, the Reagan administration looks like one that talks tough to Mr. Gorbachev but acts with far less resolution.
This is not a question of Ramboism. No sane person is asking for the Marines to be sent in. It is, however, a matter of principle and of the rule of law.
The United States has just emerged from traumatic months of spy scandals in which it is clear the Soviets have been coldly and calculatedly pillaging American defense secrets and military technology. The Soviet spies the United States catches should be held fully accountable under American law.
In other instances, the US refuses to make deals exchanging legally held prisoners for innocent hostages. In the case of Daniloff, it has bent the rules.
All compassionate Americans were eager to see Daniloff freed from his KGB cell. But journalists and Foreign Service officers and businessmen know the risks of working in Moscow. Nobody forces them to accept assignments there -- or in a dozen other dangerous capitals where Americans have elected, for various reasons, to pursue their professions.
And the fact is that by agreeing to this initial equality of trade, the Reagan administration may have made the risk greater for journalists and other Americans serving abroad in the future. What has worked once may be attempted again.
There are thoughtful people who argue that the Daniloff case could not be allowed to jeopardize summit preparations, that there is too much at stake in Soviet-US relations, that it is important to keep on talking. Well, there are many channels other than a summit through which to communicate to the Soviets.
The message should be clear: If the record of the new Gorbachev regime on other issues is to be surrounded by as much deception, trickery, and dishonesty as has been evident in the Daniloff affair, summitry has little point.