The major European allies have moved closer to President Carter's position on Western economic and diplomatic sanctions against Iran and are expected to adopt at least partial sanctions at a foreign ministers' meeting early next week, according to government sources in several capitals.

Although remaining divided on the extent and precise timing of the imposition of sanctions, the allies have now hardened their positions.

West Germany reportedly is planning to support the original U.N. Security Council sanctions order, while British officials favor at least some of the sanctions. The British, however, are proposing that the Common Market countries move to sanctions after a planned series of steps to end the Iranians crisis.

Even France has agreed to issuing a strong warning to the Iranians.

Portugal today banned trade with Iran, becoming the first Atlantic ally to impose major economic sanctions, as it joined the U.S. efforts to win the release of the 50 hostages held at the American Embassy in Tehran since Nov. 4.

West German officials have indicated they will ask the foreign ministers of nine European Common Market nations next week in Luxembourg to impose much or all of the proposed U.N. sanctions order, which the Soviet Union vetoed in January. President Carter has used the order as the basis for his requests for allied backing of sanctions imposed by the United States.

The West Germans and Common Market officials in Brussels believe this can be done under the European Economic Community's powers to regulate European trade, supplemented if necessary by speedy legislative changes by member nations.

Besides supporting at least some of the proposed sanctions, Britain favors some other unspecified "political" steps, officials indicate.

The British are proposing that the first of their staged action plan would be a statement issued at the Luxembourg meeting telling the Iranians of the European intention to impose sanctions soon if Tehran does not take concrete action to free the hostages.

The French Cabinet reportedly decided yesterday that France will urge the foreign ministers to go no further next week than issuing a strong warning to Tehran specifically threatening European "economic and political" sanctions if no progress is made in solving the hostage problem.

This still leaves the French far from the West German and British positions, although a compromise may be reached between the French and British proposals.

Indicating that France remains wary of tying itself too much to open-ended group action. French Foreign Minister Jean Francois-Poncet said in Paris today that France "must decide for itself the opportune moment for the measures it judges most appropriate and effective" to take in the Iranian crisis.

Italy may be the most reluctant among the major European allies to agree to sanctions because, as an Italian official said today, "We are the most exposed, besides possibly Japan."

More than 1,600 Italians are in Iran working on more than $3 billion worth of construction projects. Italian sources said today that only a small portion of this investment is insured or covered by Iranian assets in Italy.

Most of the smaller Common Market countries are expected to agree with any consensus the others reach next week or at the EEC summit in Luxembourg a week later.

Portugal's announcement that it will ban all trade with Iran means that the oil-poor nation will lose a major source of its petroleum. Figures for the third quarter of 1979 showed it obtained 21 percent of its oil supplies from Iran.

For the world in general, however, the threat of the loss of Iranian crude oil is not considered to be acute. One European oil industry spokesman said the effect of a cutoff of Iranian oil would be "small . . . minimal."

If the Iranian spigot were cut off to the allies, Japan would probably be the hardest hit, since it imports from 10 to 13 percent of its oil from Iran. Nineteen industrialized nations, including most of the allies, have signed an agreement, however, that triggers as sharing of available supplies once any country finds a 7 percent shortfall.

The Europeans "have moved some distance but not quite so far as the Americans want them to go," said one source close to discussions of the European position at the EEC headquarters in Brussels.

West Germany officials have been hinting broadly they are ready to impose trade and banking sanctions if the Common Market countries fail to agree on at least limited sanctions.

Both West Germany and British officials are known to be concerned both about the threat to the unity of the Atlantic alliance that the Iranian crisis poses and about the possibility that President Carter might take military action against Iran that could endanger world peace.

British officials have reluctantly shifted their position from resisting sanctions because of the damage they could do to an already ailing British economy and the possibility that they would drive the Iranians further away from the West into the arms of the Soviet Union.