The United States presented its European allies and Japan today with a list of economic and diplomatic actions President Carter wants them to consider taking in support of U.S. sanctions against Iran.

The list, delivered to allied foreign ministers by U.S. ambassadors in their capitals, reportedly includes limiting or cutting off trade and financial transactions with the Iranian government. The allies previously have resisted taking such steps.

The Carter administration specifically asked all allied governments to downgrade their diplomatic representation in Tehran in protest over the continued detention of 50 American hostages seized by Islamic militants last Nov. 4.

[In Washington, senior U.S. officials said Carter was seeking "collective action" against Iran to head off a more dangerous situation if the hostage crisis remains unresolved but that the allies are not expected to match each U.S. step. Story on page A16.]

The immediate reaction in European capitals and Tokyo was one of a sympathetic understanding combined with renewed fears of economic difficulties and potential retaliatory cutoffs of Iranian oil supplies.

Iran's Oil Minister Ali Akbar Moinfar reiterated in Tehran today the warning to cut off oil from "any country which participates in economic sanctions."

After helping convince Carter to delay imposing economic sanctions earlier this year, allied officials did not appear eager to confront the problem again. t

U.S. economic sanctions against Iran are by themselves largely without impact on either country because most bilateral trade has already stopped. But many Western European nations and Japan still carry on significant trade and financial dealings with Iran and import considerable amounts of its oil.

Although allied leaders were notified over the weekend of Carter's actions, government spokesmen in Europe and Japan said today they would carefully consider the U.S. request.

Sources in Britain, West Germany and Italy suggested that the nine European Common Market countries were expected to take a joint decision on the issue, saying only their united reaction would have any validity. Officials speculated about possibilities of gradual withdrawal of diplomats, either in terms of overall staff reductions at their Tehran embassies or of ambassadors alone.

In Italy, an official of Agusta Co., which produces several types of American aircraft under U.S. license, said today the Italian government has "suspended" the delivery to Iran of several Chinook helicopters and 15 cases of spare parts for other helicopters already delivered to Iran.

Agusta's general manager Piero Fascioni, said the suspension was temporary and did not mean that Italy had set up any kind of embargo. It is believed that Agusta officials feared the revocation of the U.S. licenses if they disregarded American feelings on so sensitive an issue.

In Bonn, West German sources said the government is more sympathetic toward Carter's economic sanctions against Iran because of the hostages than toward imposing sanctions against the Soviet Union in response to the Afghan invasion.

The president of the West German Federation of Trade and Industry, Otto Wolf von Amerongen, last week said he thought West Germany "would respond positively" in the "special case" of the 50 hostages because "lives were directly involved and the United States must be helped."

Japanese Foreign Ministry officials said today that the Tokyo government promised "general support" for Carter's decisions. But the Japanese, who import 10 percent of their oil from Iran, are clearly fearful of getting entangled in the U.S. sanctions.

Well-informed British sources said today there were still major legal and economic problems to overcome before Britain or other European allies could join in economic sanctions against Iran, although they understood that Carter was forced to act and needs allied support.

Britain still imports 7 percent of its oil from Iran, despite its own North Sea oil resources. It also still carries on other trade with Iran, much of it automobiles whose parts are made here by Chrysler UK for assembly in Iran.

But most important is the extensive banking done here by Iran, part of Britain's vital international banking business. British bankers strongly oppose and could possibly stop in the courts, or Parliament any action, according to one source, that could "harm confidence in London as a banking center by antagonizing a big petro-dollar customer like Iran."

Prime Miister Margaret Thatcher, who promised strong support for Carter during the Iranian crisis, has said she did not believe she could push through Parliament legislation imposing trade and banking sanctions.

British and other European officials have told the Carter administration that imposing trade and legal sanctions was legally difficult without a United Nations order. These officials also contend that such punitive measures would further alienate the Iranians from the West.

Washington Post correspondent William Chapman reported the following from Tokyo.

The U.S. decision to sever relations with Iran evoked a sympathetic response from Japanese officials but it also revived fears of possible danger to Japan's oil supplies.

Foreign Minister Saburo Okita said Japan "understands" the circumstances of Carter's latest effort to pressure Iran to release the U.S. hostages, whose imprisonment he called "an outright violation of international law."

It is "regrettable that it came to this situation" after months of "self-restraint" by the United States and the assistance of a U.N. commission which tried to negotiate the hostages' release, he said.

The major concern in Tokyo, however, was that the revival of American economic pressures on Iran might entangle Japan again in the issue of sanctions against a country that provides this country with 10 percent of its oil. "I think there will be some hard times," said one government official.

It could also revive pressure to discontinue work on a huge petrochemical plant being built in Iran with Japanese industrial and government assistance.

Ambassador Mike Mansfield this afternoon explained Carter's message in a conference with Vice Foreign Minister Masuao Takashima. Officials said later Mansfield sought Japan's general cooperation but gave no details.

According to Foreign Ministry sources, Takashima promised "general support."

Japan fears that if it joined in specific pressure on Iran, that country would act quickly to cut off its oil supplies. In an agreement worked out last fall, Japan this year will buy about 530,000 barrels a day from Iran, 10 percent of its total imports.

The other major issue is Japan's support of a huge petrochemical plant being built at Bandar Khomeini, in southern Iran. Nearly complete, but stalled for months by revolution and politics, it is a project that Iran has made a test of Japan's support.

Iran recently insisted that construction resume immediately and even laid down the rule that at least 300 workers be sent to the site. It has accused the Japanese companies of footdragging because of American pressures and warned that Eastern European aid would be sought to finish the plant if the Japanese assistance did not come through.

Seventy Japanese workers are at Bandar Khomeini now and 20 more are on the way. Another 210 are to go in May to comply with the Iranian ultimatum. To finish construction, the Japanese government and private companies have pledged about $2.7 billion.