MOSCOW, FEB. 22 -- The United States and the Soviet Union ended two days of intensive presummit diplomacy today declaring they had made modest strides toward a treaty slashing strategic nuclear arsenals but with no visible movement on the urgent issues of Afghanistan and the Persian Gulf.

No triumphs or breakthroughs were announced, but neither was there any sign of a roadblock in the way of a meeting of President Reagan and Soviet leader Mikhail Gorbachev in Moscow in late May or early June.

"You can rest assured the visit will take place," Soviet Foreign Minister Eduard Shevardnadze told reporters, adding that firm dates for Reagan's trip to the U.S.S.R. will be set when the Soviet minister visits Washington for the next round of presummit negotiations March 22 and 23.

The central advance in the strategic arms negotiations was an agreement to develop three detailed documents on verification of the pact by the time of next month's Washington talks. U.S. officials hailed this as a necessary and important sign of determination on both sides to tackle this subject early, but they conceded there was no guarantee of agreement on the substance of the complex and sensitive issues involved.

Gorbachev's decision, announced two weeks ago today, to set a date for the withdrawal of Soviet troops from Afghanistan precipitated long discussion of the Soviet and U.S. positions on the way to end the eight-year-old war.

Secretary of State George P. Shultz, in the most positive U.S. statement to date on the Gorbachev declaration, told reporters that "I don't have the slightest doubt the Soviet Union has decided it wants to leave Afghanistan." He added there is "a very good chance" the Soviet troops will be gone by the end of 1988 -- 3 1/2 months ahead of the schedule announced by the Soviet leader.

The key questions of the details of the pullout, its relationship to the establishment of a new interim government in Kabul and U.S. acceptance of a pledge not to supply further military aid to the Afghan resistance will be addressed in U.N.-sponsored talks to convene in Geneva on March 2.

Details of the Soviet pullout plan were not presented to the Shultz team, but were promised in the Geneva talks. "The proof of the pudding will be in the eating," said Shultz of the prospect of receiving this plan.

Shevardnadze, in a similar display of hopeful skepticism, quoted Shultz as saying that "the U.S. administration will do its best to assure that the current {Geneva} round is a final concluding round" of the Afghan negotiations -- "so let us believe him."

Shultz did not repeat a statement made several times recently that a cutoff of U.S. military aid to the Afghan insurgents must be accompanied by the ending of Soviet military aid to the Moscow-backed Afghan government.

Shevardnadze said Moscow "cannot reasonably disregard" its obligation to aid Afghanistan under a 1921 treaty signed by Lenin. But he added that it is also possible no more arms supplies will be needed after the Soviet pullout.

U.S. officials shed no new light on their relationship to Pakistan's decision not to sign the Geneva accords unless an interim government is established in Afghanistan first. Undersecretary of State Michael H. Armacost goes to Pakistan Tuesday to discuss pending questions. Pakistan contends that without an agreed-upon government in Afghanistan, the 3 million Afghan refugees in Pakistan will not go back.

There was no agreement on the issue of a U.N.-sponsored arms embargo against Iran, which the United States hopes to bring to a vote in the Security Council by next Monday, U.S. Ambassador Vernon Walters' last day as chairman.

A senior U.S. aide said Washington will "intensify discussion" among Security Council members with the aim of a quick vote for sanctions intended to penalize Iran for continuing the war in the Persian Gulf. He volunteered, though, that in the absence of a consensus, the vote might be postponed.

Shevardnadze said the Soviet stand on the Iran sanctions resolution is "a question for tomorrow," but he seemed to endorse the "detailed and active" negotiations under way in the Security Council.

The Soviet news agency Tass said on this point only that Gorbachev promised to "discuss some ideas" Shultz had advanced on the Persian Gulf diplomacy. No details were given.

On the Arab-Israeli issue, Shultz gave a full briefing on his plans for a new mission to the Middle East beginning Thursday, two days after he returns from the Soviet Union.

Shultz seems to have found little enthusiasm for his initiative among the Soviet leadership, which has been advocating an international peace conference in which Moscow would play a leading role. Gorbachev was quoted by Tass as telling him that the U.S. plan is "not in keeping with the principle of taking into consideration the interests of all the sides involved."

Gorbachev said the Soviet Union does not object in principle to the "intermediate measures and steps" Shultz has in mind on his trip, although the Soviet leader said they can yield results only "in the context" of an international conference, which is strongly opposed by Israeli Prime Minister Yitzhak Shamir.

Shultz had not been seeking active Soviet participation in his plan but had hoped for some sign Moscow would not interfere.

Shultz reported that discussions also were held on Angola, Central America and Korea, but there was no report of significant progress.

On strategic arms, senior U.S. negotiators described the work plan on verification issues as an important practical step toward meeting the objective of the two leaders to sign a far-reaching pact during the Moscow summit.

The U.S. negotiators said that as a result of the discussions here, there is probably a greater chance to meet this goal than before, but they would not say how big a chance that is.

The three documents that the two sides have pledged to develop in the next month are protocols, or guiding regulations, on inspection and on conversion or elimination of strategic offensive arms, and a memorandum of understanding on the numbers, types and locations of weapons involved.

The longstanding and basic dispute over strategic defense and its relationship to offensive arms had seemed to be placed on a back burner by accommodations reached in the Washington summit in December. But in recent weeks the two sides began hurling charges at one another on these issues again, each claiming the other was departing from what had been done in Washington.

Participants on both sides said the current discussions resulted in agreement to go back to the language and spirit of the Washington joint statement, which was widely interpreted as an agreement to disagree on space defenses.

On the controversial subject of nuclear testing, the two sides agreed to draw up verification plans for implementing the 1974 threshold test-ban treaty and the 1976 peaceful nuclear explosions treaty.

Such plans, if accepted, would permit the U.S. administration to ask the Senate to ratify the two treaties, which have been awaiting Senate action for years.

The two sides also discussed ratification and enforcement plans for the treaty on intermediate-range missiles signed in Washington.

The Soviet Union plans to withdraw nuclear missiles from East Germany and Czechoslovakia that were part of the arsenals earmarked to be scrapped under the INF treaty even though ratification is still pending, Soviet Defense Minister Dmitri Yazov said in a separate speech.

At a ceremony marking the 70th anniversary of the Soviet Army and Navy, Yazov said Soviet withdrawals of SS12 short-range missiles would start in February. There are 54 SS12s in East Germany and 39 in Czechoslovakia, according to western records.