Summit moves nearer. LESSONS FROM DANILOFF-ZAKHAROV AFFAIR. Desire for a summit appears to be the force behind Daniloff release. But both sides are still learning how to avoid pitfalls en route

Summit hopes did it. Diplomatic observers say it was the overriding desire of both the Soviet Union and the United States to hold a second summit meeting that drove the effort to resolve the Daniloff-Zakharov affair. With this awkward situation removed, the prospects of a summit and of progress toward an arms control agreement are greatly increased.

``This will put the summit back on the rails,'' a State Department official says.

Whether the deal the US struck with Moscow creates a negative political fallout for President Reagan remains to be seen. The President is given high diplomatic marks for his restraint throughout the affair, but he has taken a great deal of political heat from conservatives inside and outside the administration.

As Americans quietly cheer the release of Nicholas Daniloff, the Moscow correspondent of U.S. News & World Report arrested for alleged spying, diplomatic analysts are attempting to draw lessons from the incident. They warn that if Moscow and Washington do not learn from this experience, they will risk further endangering the process of stabilizing the US-Soviet relationship and reducing the dangers of nuclear confrontation.

Both superpowers are seen to be responsible for this latest crisis by shortsighted policies or inadequate mechanisms for making sure that summitry is not undermined by unforeseen developments.

To begin with, why did the United States arrest Soviet United Nations employee Gennady Zakharov on charges of espionage at this particular time? To be sure, the Justice Department was doing its job. But informed sources say that officials at a lower level did not understand the implications of the arrest in the context of superpower relations at this delicate stage. As a result, there was no opportunity to consider at a higher level what should be done.

The Soviet Union, for its part, failed to understand the extent to which the United States regards as unacceptable activity the use of Soviet employees at the UN to gather intelligence. While Mr. Zakharov may have collected only unclassfied information up to his arrest, even this made it possible for the Federal Bureau of Investigation to spring a trap on him -- and Moscow quickly reacted by grabbing Daniloff.

``The Soviets decided long ago to use UN people on things not related to their Secretariat duties, and that is a mistake,'' says Mark Garrison, a former diplomat in Moscow. ``Given all the pressure by us, they should have been able to see this coming down the road, but they probably did not focus on this at a high level.''

Each superpower, diplomatic experts say, failed to put the proper priority on making sure something does not go wrong at a crucial time. One former State Department official recalls that, during his tenure, it was a common practice for the head of the Soviet desk to meet periodically with officials of the FBI and the Central Intelligence Agency. This helped avoid Zakharov-type incidents.

``When the two sides are approaching an important opportunity, it's absolutely imperative that the administration in Washington and Soviet leaders in the Politburo follow carefully the entire relationship,'' says Charles William Maynes, editor of Foreign Policy magazine and a former diplomat in Moscow. ``Zakharov didn't have to be reeled in when he was, whatever we're doing in tracking Soviet spies, and that showed poor policy coordination.''

At press time it was not known what agreement had been reached between Washington and Moscow. The expectation here, based on scenarios aired over previous days, was that Zakharov would eventually be freed by US authorities, followed by Soviet release of several dissidents.

[According to a Reuters report, President Reagan insisted yesterday that there had been no trade-off with the Soviet Union to win Daniloff's release, and that the Soviets had been the first to back off in the confrontation.]

Discussion is already under way in this capital about whether Soviet leader Mikhail Gorbachev or President Reagan blinked first. Some experts say this represents a clear diplomatic loss for Moscow. Others suggest that a solution that enables both sides to claim success and not appear to have lost face is the best outcome.

Meanwhile, President Reagan, despite early confusing signals from the White House, is lauded for keeping cool and letting diplomacy do its work.

``Reagan deserves good marks,'' says Paul Warnke, who negotiated the SALT II agreement under the Carter administration. ``He made no intemperate statements and he got his message across through private diplomacy.''

The reasons for his restraint are clear. With Daniloff in Soviet detention, the President would not have been able to go to a summit without the subject of the arrested American newsman preempting the agenda. US participation in a summit under those circumstances also would have looked unseemly.

The Soviets, for their part, would have been utterly on the defensive at the summit, making progress on substantive issues difficult.

President Reagan had hoped to be the first to announce Daniloff's release when he addressed a cheering crowd at a campaign appearance in Kansas City, Mo., Monday. But he had already been scooped by Western reporters in Moscow, who saw the happy Daniloff leaving.