The continuing seige of the U.S. Embassy here by Islamic militants has propelled Iran's mired revolution into a new, more radical phase. Iran has become a textbook example of runaway revolution.

Anti-Americanism is the chosen instrument of the radicals who have succeeded in using the embassy seige to force Prime Minister Mehdi Bazargan from office. Bazargan's commitments to reform, democracy, even Western-style economic efficiency are being swept away by the new revolutionary tide.

Political insiders readily, if privately, admit that anti-Americanism is a powerful tool in the hands of those who are seeking an attempted return to an idealized version of 7th century Islamic theological rule.

Ayatollah Ruhollah Khomeini may well have decided that the radicals' frontal assault on the nation that supported the deposed shah throughout his reign was more effective in rallying the nation than setting rich against poor or other options at his disposal.

There are hopes that the militants may be willing to separate the fate of the hostages from the general policy of anti-Americanism.

Abol Hassan Bani-Sadi, newly in charge of foreign affairs for the ruling Revolutionary Council, hinted as much in an interview today with the Paris daily Le Monde.

He said that "it's up to the United States to take the initiative to end the crisis" that Iran contends the Carter administration set off by admitting Shah Mohammad Reza Pahlavi to America.

He insisted that the hostages' "liberation depends on the United States," and warned that with the present state of emotionalist fervor "no Iranian unilaterally will be able to take such a measure" -- meaning freeing the hostages.

"In the interest of all parties an initiative must be taken to give Iranians satisfaction," he said, as if to suggest the official demand for handing over the shah might be negotiable.

By indirection some diplomats and analysts here believe, the United States must make some kind of gesture, perhaps an admission of guilt concerning American policy ever since 1953. That is when the Central Intelligence Agency helped stage a coup that put the briefly deposed shah back on his throne.

"The problem is that Khomeini and Carter live on different planets," a diplomat remarked. Carter is confronted with symbolism, Third World symbolism. He's being asked to settle a material problem regarding men's lives in exchange for words, albeit difficult words. He is also dealing with a leader whose successful stock in trade has been never to compromise, whether in dealing with the shah or anyone else he feels is in his way."

No one here thus foresees any easy solution to the hostage problem.

Like so many Third World radical leaders before him, Khomeini is asking basically for redress of abased national dignity at the hands of what is comparable to a former colonial power.

These feelings of humiliation date not just from the past 25 years, but also from many, many years of domination, first by the Soviets, then by the British.

In an election year, Carter's problem, diplomats here fear, is that he is pressed for time, while Khomeini feels time is on his side.

However dangerous their predicament is, the U.S. diplomats' incarceration does differ from comparable hostage cases elsewhere in one important aspect.

Iranian officials including Bani-Sadr have ruled out executing the hostages, and since Khomeini has put his official mantle of authority over the embassy occupation by radical students, the usual tension about forcing the hostages' release is absent.

For now, the policy has rallied support in a nation that only a week ago appeared to be slowly going to pieces.

"Will and obstinacy are being shown capable of embarrassing a superpower," a diplomat noted recently. "That proved a popular thing when Khomeini drove out the shah in January, and now again."

In his interview, Bani-Sadr promised:

Radical change in the Iranian military's organization, training and technical dependence "to free us from the stranglehold" and to effect a "definite break with its former [American] tutors.

An "active foreign policy aimed globally against the hegemony of the superpowers, but especially against the principal enemy, the one with which we are in permanent confrontation" -- once again meaning the United States.

In this light some Iranian radicals have claimed "equilibrium" in Iran's recent abrogation of the 1959 U.S.-Iranian defense treaty that extended the American nuclear shield to Iran and the 1921 Soviet-Iranian treaty that allowed Soviet intervention in Iran's affairs if Iran became a "base of operations against Russia."

Analysts here believe that the Soviet Union is being spared criticism at present largely because Iran fears provoking the Kremlin into providing the rebellious Kurds with arms as happened after World War II.

At home, Bani-Sadr promised a "purge of the state machine," whose employees, often "corrupt or inefficient," absorb the "totality of our oil revenues."

"Our objective," he said, "is to transfer four or five bureaucrats to productive sectors," as well as favoring the countryside over cities, especially Tehran, whose growth even the shah had sought to limit.

Anti-Americanism is likely to remain a popular rallying cry as the revolution plunges ahead.

President Carter's national security adviser Zbigniew Brzezinski met with Bazargan and foreign minister Ibrahim Yazdi 10 days ago in Algiers, before they were ousted, and had warm praise for them. Whether this was the kiss of death to the Bazargan government, as some analysts claim, is open to question.

In any case, the moderate, Western-oriented Bazargan camp was increasingly at loggerheads with the radical religious leadership in the weeks preceding the government's formal resignation.

Polarization was growing, fed by unemployment, failure of manufacturing to regenerate, the often tough-then-soft policy toward the rebellious Kurds and arguments over traditional vs. Islamic justice and the role of theocratic rule.

The Bazargan government, elite, upper middle class, relatively moderate, and intellectual (except for the pro-Khomeini Communists) and powerful Ayatollah Kazem Shariatmadari blamed the clerics for the meddling and called for an end to the revolution. The radical clerics in turn, admitted the mess, but blamed it on Bazargan, a manager incapable of the political will to push ahead with the revolution.

The radicals' chances of success are clouded most immediately by the civil war atmosphere among the populous non-Persian national minorities.

The problem is most acute with the Kurds in western Iran, then with the Arabs of oil-rich Khuzestan in the south. There is also a potentially explosive situation among the Azerbaijanis, loyal to Shariatmadari, along the Soviet border in the northwest.

Together the minorities make up an estimated 50 percent of what the shah used to call the Persian empire. They have long complained of political and cultural domination by the Persian heartland.

While the top 20 percent of Iranian society may be against them, the radicals have some potentially important backing. It includes a divided petty bourgeoisie, peasants happy that wheat prices have doubled and absentee landlords' fields have been taken over, and a working class, with the unemployed angry, but job holders happy.

For all these elements, anti-Americanism is as solid a cement as the regime can now muster.

Analysts here are convinced that despite insults and criticism, however, American strategic interests will be taken into account by Tehran.

Such is the lot of a superpower -- all the more so since Iranians, especially religious leaders, traditionally have reserved their greatest suspicion for their Soviet neighbors, with whom they share a 1,600-mile frontier and much unpleasant history of Russian intervention.