The one lane metal bridge here between Iran and the Soviet Union is quiet these days despite Moscow's offer of land routes across Soviet territory to beat Western economic sanctions and a possible U.S. sea blockade.

Iran has not jumped at the offer. Hassan Zahmatkesh, the mayor of this small border city said that trade with the Soviet Union has dropped since the Islamic revolution 16 months ago, and that the number of trucks coming across the bridge from the Soviet Union has not increased.

Only a handful of big trucks carrying cargo from the Soviet Union were seen this week during a trip on the pitted two-lane road that runs along the Caspian Sea from here to the center of Iran.

The Soviets are trying to cash in on anti-American sentiment in Iran by offering strong support to beat the sanctions. Eastern Bloc countries have also emerged -- with Moscow's evident blessing -- as major trading partners with Iran, buying an increasing amounts of Iranian oil in exchange for the industrical goods, food stuffs and technical expertise that Iran needs.

In Tehran, Bulgarian cigarettes areappearing on the streets as the supply of more popular American Winstons have dwindled and newsletter producers are complaining that they can only get Romanian or Czechoslovakian mimeograph stencils.

It is still unclear, however, whether the Soviets are succeeding in getting closer to Iran's Islamic republic, where the official line as set down by revolutionary leader Ayatollah Ruhollah Khomeini is "Neither Western nor Eastern."

Moscow, however, has gained a major victory over the United States in that Iran no longer acts as America's policeman in the Persian Gulf. The U.S. electronic monitoring stations that used to keep watch on Soviet missile activities now are idle.

The Soviet Union, which is likely to become an oil importer by the end of the 1980s, also has gained confidence that Iran will be a possible source of oil for itself and the Eastern Bloc nations.

But while an Iranian trade delegation is in Moscow trying to forge new links in that area, Iran's foreign minister, Sadegh Ghotbzadeh, will meet in Geneva with other Islamic ministers who are seeking to get the Soviets to withdraw their troops from Afghanistan.

Iran also has refused to sell the Soviets natural gas for the past three months -- although it has no other customers -- because Moscow will not pay the world price.

"As an assertion of our independence, we are burning our gas," Ghotbzdeh said.

So while America remains "the great satan," the Soviet Union is viewed by many Iranians as "the lesser satan." They are suspicious of Soviet motives, remembering that in 1920 and after World War II, the Soviets tried to annex parts of Iran. "Godless communism" is also feared as an enemy of Islam.

If Iran has been schizoid in its recent relations with the Soviet Union, Moscow too, has been ambivalent in its wooing of the Islamic republic.

Along with Washington, Moscow appeared surprised by the rapidity of the Islamic revolution that overthrew the shah. Although the Soviets usually are quick to support national liberation movements, they took their time in this one.

At the same time, the Soviet's appeared fearful that Iran's Islamic resurgence would spread across the border to its own Islamic republics.

While opposing Western sanctions and any U.S. military intervention, in Iran, the Soviets were reported to have vehemently opposed the taking of the American hostages at the U.S. Embassy last November.

Last month diplomats in Tehran reported that the Kremlin called in Iran's ambassador to Moscow to urge that the hostages be freed.

Meanwhile, the Soviet Union campaigned vigorously in the last year to win Iranian friendship. Playing on the anti-American sentiment in Iran, the Soviets said that it was forced to invade Afghanistan to protect it from United States forces.

This territory bordering the Caspian Sea, is a stronghold of leftist sentiment in Iran. Posters for the pro-Moscow Tudeh Party and the leftist Mujahedin-e-Khalq are much more visible here than in other sections of Iran.

Otherwise, there are few signs of Soviet influence on the border. Some residents here admit to wading across the Aras River to collect wood on the Soviet side, where a waist-high barbed wire fence serves as the border. But the wood-gatherers said that there are higher fences and border guards hidden in the woods.

The trucks that lumber across the bridge from the Soviet Union come from all over Eastern Europe. Three flat-bed trucks carried large containers marked "USA," but there was no way to tell whether the cargo actually came from America.

Astara's Mayor Zahmatkesh said that Soviet trucks often travel in convoys of 10 with police escorts to discourage attack.

There are signs of increased soviet trade in the Caspian Port of Bander Anzeli (formerly Bandar Pahlavi), 80 miles southeast of here.

Nine Soviet ships were docked in triple layers Tuesday morning, unloading cargos of lumber and steel. Ali Ansari, the governor of Gilan Province, said the ships also bring milk power and fertilizer to Iran, but generally return empty to the Soviet Union.

Ansari said longshoremen now are handling 4,5000 tons of cargo a day compared to about 2,000 tons in the past.

Yet trade with the Soviets now is far less than it was when the shah was in power. In 1977, there was more than $1 billion in commerce between the two countries and Iran was the Soviet Union's largest nonmilitary trading partner in the Third World. Last year, trade was less than half that amount, according to Moscow sources.

While the Soviets are pushing trade, their armed might remains close to Iran's borders in both the Soviet Union proper and Afghanistan.

But residents do not appear concerned about the Soviet military.

"We are not worried about a Soviet invasion," Ansari said. "We believe in God and if some one tries to invade, we will fight against him. We are not scared of being killed because martyrdom is an honor."