IRAN FLEXES ITS MUSCLES. Tougher times ahead in the Gulf. Soviets court Tehran in effort to capitalize on US-Iran tensions

The Soviet Union is showing signs of altering its position on the Gulf war by moving closer to Iran, European and Arab diplomats say. ``The Soviets proposed in vain to the Reagan administration to hold bilateral talks on the Gulf,'' a Paris-based Syrian diplomat says.

``Moscow now realizes that the United States is going it alone in the Gulf, and it thus tends to analyze the crisis in classic terms of competition between the superpowers. The Soviets, in spite of the fact that Iraq is their traditional ally, are pretty much tempted to side with Iran in its present conflict with the US.''

But the Soviet Union remains opposed to an Iranian military victory over Iraq, the diplomat adds, and would like peace to be restored quickly in the Gulf without there being a victor or vanquished.

Yuli Vorontsov, Soviet deputy minister of foreign affairs, is now on his second trip to Iran and Iraq in two months. He arrived in Baghdad Friday and was expected in Tehran within days. Western diplomats in both capitals say Mr. Vorontsov is likely to offer new Soviet proposals on the crisis. On his June visit, he is said to have invited both countries' leaders to Moscow for talks.

The recent change in Soviet attitude is already reflected in the Soviet press. ``The US is staging a military operation against Iran,'' Pravda wrote last week in an editorial on US escort of reflagged Kuwaiti tankers. The press has also refrained from writing vitriolic editorials accusing Iran of responsibility for prolonging the war, which it has done in the past.

The Iranians have reacted quickly to Moscow's new mood and have been toning down their criticism of the Soviet Union.

On July 28, in a two-hour message to Iranians taking the annual pilgrimage to Mecca, Ayatollah Ruhollah Khomeini said, ``We'll force both superpowers to kneel down.'' But Western observers in Tehran noticed that, in the rest of the message, the Ayatollah repeatedly castigated the US government, but remained discreet on the subject of the Soviet Union.

An Iranian diplomat contacted in Bonn on Friday said his government seriously believes the Soviets have adopted a new policy in the Gulf that is ``more positive'' than that of the US and its allies, France and Britain.

This diplomat points out that the Soviet Union now:

Backs Iran's proposal that freedom of navigation in the Gulf be ensured only by bordering countries.

Supports Iran's request for a cease-fire limited to Gulf waters.

Has reduced its arms shipments to Iraq.

Has convinced Iranian leaders it is serious about getting its troops out of Afghanistan.

A senior European diplomat dealing with the Gulf region says he was surprised when a Soviet diplomat visited him a few days ago and insisted his country now supports a truce in the sea war.

``When I told him this would give Iran an advantage and could thus hardly be accepted by Iraq, the Soviet diplomat replied that, under the present circumstances, no military intervention - save a full-scale invasion of Iran that would require the use of nuclear arms - will force the Iranian leadership to negotiate. He said his country therefore believes new diplomatic ways should be explored in order to find a peaceful solution to the present crisis.''

The European diplomat concluded by saying the Soviets are apparently irked by what they perceive as Iraqi and Kuwaiti maneuvers to force an increase in the US military presence in the Gulf, something Moscow adamantly opposes.

Iranian diplomats say the turning point in Soviet-Iranian relations apparently came June 14 at a lengthy meeting in Tehran between Vorontsov and President Ali Khamenei. A few days earlier, Iranian Revolutionary Guards had launched a raid against one of the three Soviet tankers leased to Kuwait. In the course of the meeting, Vorontsov reportedly promised that the Soviet Union would not increase the number of its warships (now three) in the Gulf, and would support Iran's request for a cease-fire at sea.

During this week's visit to Tehran, Vorontsov is also expected to discuss the possible reopening of a pipeline linking Iran's gas fields to Soviet southern republics.

The pipeline was closed by Iran in May 1980 after a dispute over prices. Iran sought unsuccessfully to have it reopened in February 1986. Western diplomats say a reopening of the gas link would signal a major change in Moscow's attitude toward the Gulf war, for it would provide Iran with important new financial resources.

Moscow's new approach to the Gulf crisis has been quickly followed by its Mideast friends. Syria, for example, which since January had seemed to cool its support for Iran, on July 12 dispatched its foreign minister to assure Tehran of Syrian backing. Druze leader Walid Jumblatt, one of Moscow's best allies in Lebanon, on July 29 said he stands firmly by Iran and met for the first time with leaders of the pro-Iranian Hizbullah party. (Tracing the emergence of Shiite activism, Page 20.) Only weeks ago, Jumblatt was a relentless critic of ``Persian imperialism.''

Mr. van England writes on Iran from Brussels.