The countries of the 21-member Council of Europe joined today in an appeal to Iran to release the Americans being held hostage at the U.S. Embassy in Tehran.

Foreign ministers from the council's member states issued a communique following a one-day meeting in Strasbourg, France, in which they condemned the hostage-taking as a "flagrant violation of international law."

According to the communique, the foreign ministers "made an urgent appeal to the Iranian authorities to release the American hostages and put an end to a situation which dangerously impairs international relations."

The council's membership is comprised of virtually every country in Western Europe.

This city, meanwhile, is awaiting a meeting Friday between Chancellor Helmut Schmidt and visiting Soviet Foreign Minister Andrei Gromyko. Schmidt's close aides say that Schmidt is expected to point out the dangers posed by the situation in Tehran.

West Germany has been closely following the embassy siege with officials fearing that any U.S. military intervention could bring Iranian retaliation on all Westerners in Iran including 1,600 West German civilians.

The Bonn government has supported the Carter administration in the crisis and the United States has been given high marks here for its patience and restraint.

As a prelude to Schmidt's talks, West German Foreign Minister Hans Dietrich Genscher declared at a dinner for Gromyko that "the whole community of nations is challenged" by the embassy takeover. "Nobody dare remain silent," he said.

"Our thoughts go out to the people held as hostages in the American Embassy in Tehran in violation of international law. Our sympathy goes to them, and to the American people we express our solidarity. We appeal to those responsible in Tehran to free the hostages," Genscher said.

Schmidt will be the first major Western leader to meet with a top Soviet official since the Iranian militants took control of the embassy Nov. 4. The chancellor's expected message, they say, will be to stress to Gromyko that all civilized countries have to build up a wall against such irrational actions because the entire system of world equilibrium can be damaged seriously if responsible governments tolerate such acts.

Senior West German officials say they have no evidence that the Soviets have any influence with Iranian revolutionary leader Ayatollah Ruhollah Khomeini. Nevertheless, officials here believe it would be significant if Gromyko reflects a Soviet attitude in which the Kremlin feels it should do what it can in the interest of stability to keep Khomeini from escalating the crisis further. Officials here believe that Soviet stance may improve conditions in the immediate crisis and certainly in East-West relations generally.

Gromyko's four-day visit here was scheduled several weeks ago, well before the embassy takeover, and is centered mostly on questions of new NATO arms modernization plans and Soviet arms control proposals.

The feeling here, sources close to Schmidt say, is that it is very important that the United States stick to the special responsibilities of a big power, namely to act carefully and cautiously.

"Everybody knows America could destroy whatever targets it wanted to in Iran," one official said.

While acknowledging the increasing U.S. public pressure to "do something," these sources say that the vast majority of the civilized countries of the world are willing to back the United States in its present course of restraint. That backing, in the official's view, is an important asset that also acknowledgs superpower status.

"If you are going to have a military action," one top official said, "it must be successful and not just punishment, otherwise the Americans will be killed by the lunatics and innocent Iranians will be killed by the U.S. At the moment one cannot imagine a meaningful military action."

How allied governments would react to an American military action against Iran is hard to guage. Officials decline to discuss that because they claim not to know what U.S. contingency plans are and there is no indication that they are broaching their views on that question to Washington. i

It can be assumed, however, that Western European governments, and Japan as well, would view such a move as very dangerous, opening the possibility of open fighting throughout the Persian Gulf region, threatening oil supplies and trapping Westerners of other nationalities.