Western Europe and Japan designed their separate decisions to adopt phased sanctions against Iran as the basis for a strong plea to President Carter not to use military force to free the American hostages in Tehran.

The European allies decided to impose economic and diplomatic sanctions despite continuing strong doubts about the wisdom and efficacy of such measures, diplomatic sources in London, Paris, Bonn and Rome said today.

These same sources emphasized that the European decision was made primarily in response to warning from Washington that failure to follow the U.S. lead would bring a dangerous escalation of the Iranian crisis.

[From Tokyo, Washington Post correspondent William Chapman reported that Prime Minister Masayoshi Ohira was expected to tell Carter during a visit to Washington next week that the Japanese sanctions package was adopted in a bid to gain leverage to persuade Carter to exercise caution and avoid the use of force.]

Sharply conscious of the official and public U.S. perceptions that the allies have not done enough to support Carter's policy in the crisis, the Europeans felt that the only way to influence U.S. decisions is to support nonmilitary pressure on Iran.

In Bonn today, West German chancellor Helmut Schmidt received Barbara Rosen, wife of the former press attache at the Tehran embassy, in a meeting that lasted twice as long as scheduled.

"The emphasis was on seeking a peaceful solution," she said. "We agreed we didn't know where military action might lead."

Rosen, who is one of four hostages' relatives visiting Europe seeking support for the captives, said Schmidt had counseled "patience and calm."

The Europeans have said repeatedly both in public and in private that they have little faith that the sanctions will substantially alter the Iranian position toward favoring the release of the hostages.

Former chancellor of the Exchequer Denis Healy, the leading candidate to succeed James Callaghan as leader of Britain's opposition Labor Party, told Parliament yesterday that he feared the sanctions will make the situation worse, not better."

During the same debate on the European response to the Iranian crisis, Deputy Foreign Minister Douglas Hurd warned of "the immense, manifold dangers throughout the Islamic world of attempting to treat this matter in a military way."

A number of European leaders feel Carter's policy has been both ill-conceived and ill-defined, and overly influenced by the upcoming U.S. presidential elections. They fear that military action in the Persian Gulf could trigger a wider confrontation with the Islamic world or the Soviet Union, endangering both European oil supplies and, ultimately, world peace.

The allied decision early this week to approve a phased sanctions program was for many of the Europeans a major and agonizing shift in policy that came only after unmistakable messages from Washington that failure to follow the U.S. lead could threaten the Atlantic alliance and escalate the crisis.

Once they realized that Washington's strong request for European support was what West German Foreign Minister Hans-Dietrich Genscher called "a tests of the alliance's relations," the nine nations of the European Community moved with what they believed was remarkable speed to accomplish everything Carter had asked within weeks of the formal U.S. request.

Some European officials feel that the magnitude of this achievement, a unanimous approval of joint sanctions, has not been sufficiently understood or recognized by the White House and the American press, whose approval was one of the primary objectives of the decision.

"We've done almost precisely what our American friends have asked us to do," one senior British official said. "Frankly, we're a little pained at the cool reaction."

Disappointed, unease and a belief that sanctions are no the wisest way to resolve the crisis are themes that emerge from a reconstruction of the European response to Carter's request to join in the U.S. sanctions against Iran that he announced over Easter weekend.

This began a tense period for the Atlantic alliance in which many of the words and actions of both the United States and the allies appear to have been directed more toward each other than to the Iranians still holding the hostages in Tehran.

After the Soviet Union vetoed a proposed U.N. Security Council sanctions order in January, European diplomats helped talk Carter out of allied sanctions against Iran in favor of a more cautious, concilatory approach to the hostage problem.

In part this was a recognition of economic realities. After falling sharply in the early months of the Iranian revolution, Western European trade with Iran was growing again. Until recently, a significant, although dwindling, amount of Western Europe's oil came from Iran.

European officials also believe, however, that economic sanctions never really prove to be effective, as evidenced by the 15 years of sanctions against the renegade British colony of Rhodesia, now Zimbabwe, and could push Iran into a economic dependence on Eastern Europe and the Soviet Union.

They also feared that completely isolating Iran from the West would increase its siege mentality and make it even more difficult to obtain the hostages' release.

West European countries first realized that they would again have to face the difficult question of sanctions when their government leaders received a secret message from President Carter on March 25 outlining a timetable for tough new U.S. measures to try to resolve the hostage situation.

The timetable began with joint U.S.-European sanctions, according to informed sources, and ended with a mid-May deadline for progress by the Iranian government toward the release of the hostages, after which the U.S. would consider military options.

But the Carter administration soon informed the allies that it was holding back on this series of tough steps because of encouraging new developments in Iran that Carter later announced April 1, the morning of the Wisconsin primary.

Less than a week later, after U.S. hopes for the hostages' transfer to the Iranian government again were dashed, Carter announced economic sanctions and a break in diplomatic relations with Iran.

The allies were asked formally to join in these actions on April 8, when U.S. ambassadors in the capitals of the Common Market countries and about a dozen other nations delivered a detailed list of options to foreign ministers.

The mood of the American public against the allies, which now seemed to be enveloping the Carter White House, was already known to wary officials in London and Bonn who were reading leading American newspapers flown to them daily.They realized that as soon as Carter moved, they would have to go along.

Although still in disagreement with Washington over the effectiveness of sanctions and their potential harm, the West Germans had already promised Carter that they would back him and had a contingency plan ready.

In the absence of the vacationing Schmidt, Genscher chaired a Cabinet meeting on April 9 that formulated the West German assurances, which were transmitted immediately to Washington.

This rapid, discreet West German response in one of the reasons why officials there were dismayed and worried by the Carter administration's ensuing public criticism of the allies and the broadly implied threat of military action if the allies failed to respond that the president made in an interview with European journalists broadcast in Europe April 13.

For europe, and West Germany in particular, an added danger of a military confrontation in the Persian Gulf is that it could drain NATO resources away from the defense of Western Europe, Washington Post correspondent Bradley Graham reported. This concern was heightened by the U.S. under secretary of state for defense, Rober Komer, at a meeting in Brussels last week: "If we have to go off and defend Western interests in the Middle East, we would expect them to take up the slack in Europe," he said.