A warning from Helsinki's delegates. They caution against over-optimism in wake of successful US-Soviet meeting

Some top Western diplomats are concerned that too high hopes are being pinned on the November summit between President Reagan and Soviet leader Mikhail Gorbachev. That concern has surfaced here at a conference marking the 10th anniversary of the Helsinki agreement on security and cooperation in Europe. And it comes despite an apparently successful initial meeting between United States Secretary of George Shultz and Soviet Foreign Minister Eduard Shevardnadze.

Both Mr. Shultz and Mr. Shevard- nadze indicated the importance of making the summit a success. And US diplomats say that goal was ``advanced'' at the meeting.

Similarly, Shevardnadze, in a statement, also said he counted the meeting as ``a step forward'' in strengthening d'etente.

Nevertheless, some European diplomats are sounding a cautionary note.

``I think it's very important that no one should have unduly high expectations about any single meeting,'' says Sir Geoffrey Howe, the British foreign minister.

Adds West German Foreign Minister Hans-Dietrich Genscher, ``I am one of those . . . who would warn against an overburdening of this meeting with expectations.''

Part of the problem is that neither side has yet spelled out just what its expectations are.

One senior US official stresses that the main goal of the summit is to allow a face-to-face discussion between the two leaders, in order to set out the course of US-Soviet relations in the years ahead.

He adds that the US does not view the summit as imposing an ``artificial deadline'' to reach any agreements between the two countries that could be formally signed by Mr. Reagan and Mr. Gorbachev.

On the other hand, some US diplomats indicate that if agreements are ready to sign, then the summit might be a good occasion to adopt them formally.

Some possible agreements include the opening of consulates in Kiev and New York, an air safety agreement for the North Pacific, and a cultural exchange agreement.

But other diplomats note that none of these agreements -- even though each is important in its own right -- really provides a rationale for a summit.

The Soviets may not see it that way. Anatoly Dobrynin, the Soviet ambassador to the US, told reporters at a reception that his country was ``looking for something big'' at the summit. He also indicated that the signing of minor accords would not be enough.

Privately, Soviet officials earlier indicated that the two men should sign an agreement promising not to be the first to use nuclear weapons. But US officials say such a ``declaratory'' agreement would be practically meaningless, because it can't be monitored or enforced and can easily be broken at any time.

Both the US and the Soviets indicated that nuclear arms control would inevitably be the major topic at the summit. But both sides admit they are at an impasse at the Geneva arms control talks.

Notably, however, the Soviets did not use the meeting with Shultz to press for an end to research on the Reagan administration's Strategic Defense Initiative -- the so-called ``star wars'' program. SDI did come up for discussion, according to US State Department officials, but not in detail.

US officials say they are still unclear whether the Soviets might be willing to compromise on SDI, perhaps by allowing some forms of laboratory research but banning construction and testing of prototype weapons.

US arms control adviser Paul Nitze attended the Shultz-Shevardnadze meeting, as did Soviet arms control negotiator Yuli Kvitsinsky. Neither man spoke, however, according to participants.