West Germany is prepared to break Common Market ranks and side with the United States, apparently irritated by the reserved response of its European partners to American retaliatory measures against Iran.

Worried about recent strains in U.S.-European relations, senior Bonn aides say privately that West Germany will join the United States in taking economic action against Iran, even if other European nations refrain.

At the same time, the aides decline to say specifically just how far Bonn might go in cutting trade and diplomatic ties with Iran. Rather, their remarks appear to be carefully phrased to pressure other allies into endorsing at least limited sanctions, on the expectation that a coordinated response among the nine European community countries can be worked out that is sufficiently supportive of the American position.

What is significant here is the impression Bonn officials are seeking to create of West Germany assuming an openly leading role -- and leaning on its partners -- in a delicate European political situation. Bonn has traditionally preferred to take a more reserved posture, seemingly reluctant to exercise its growing political clout.

Reportedly behind Bonn's new offensive is the sense that U.S.-European relations have been damaged in recent months and cannot afford further serious strain. Foreign Minister Hans-Dietrich Genscher is said to have called on his European counterparts during their meeting in Libson yesterday to show active support for the tough U.S. measures.

The stance contrasts markedly with the resistance Bonn has shown toward U.S. economic sanctions against the Soviet Union in response to the invasion of Afghanistan.

But the West German government, having experienced a wave of terrorist activities in months past on its own soil, has from the start been more sympathetic with the U.S. plight in Iran.

Bonn has also been quietly reducing its own economic exposure in Iran during the past year and, having anticipated sanctions, is said to be prepared to institute them.

Aides here are critical of Britain and Italy for claiming that legal obstacles prevent them from adopting economic sanctions against Iran. Bonn officials say that the Treaty of Rome, which established the Common Market, includes two clauses that should provide sufficient legal grounds for European member nations to cut trade.

West Germany has its own law permitting the government to restrict trade when national security is at risk or in the event that international law has been violated.

Other European officials sounded somewhat doubtful about the real extent of Bonn's committment to the American course, suggesting that the Germans may simply be eager through their statements to alter their image in the United States as a not-so-reliable ally.

Indeed, Bonn did seem intent today on deflecting U.S. criticism. Government spokesman Klaus Boelling told a press conference that criticism yesterday by President Carter of the response from some of the European allies could not have been intended for Bonn. "We haven't the slightest reason to wear a cap that doesn't fit," he said.

At the same time, Boelling said there would be no decision by the Bonn government on imposing sanctions until European ambassadors returned to their capitals from Tehran for consultations following the decision taken by Lisbon.

Nevertheless, he said that while countermeasures against Iran would be more effective if taken in unison, there was no reason "in principle" that a country could not act on its own.

In the past, this principle has been overridden by the higher principle of unity of action within Western Europe, which has sometimes provided a convenient rationalization for inaction. Moreover, West Germany's own allegiance to the United States has been tempered in recent years by strengthened ties to France in an effort to strike a more independent European course.

This time, West German officials say they cannot afford to remain passive.

While signaling support for sanctions, Bonn officials reiterate their view that such measures will not be effective in winning the release of the hostages. If they go along, it will be out of friendship and partnership rather than out of agreement on tactics.

A number of proposals for joint action have been floated in West European capitals this week, among them a gradual reduction of staff in embassies in Iran and a stop in the sale of spare parts for Iranian oil and transportation systems. Stronger measures risk potential disruption of Europe's already slack economics or a cutoff of Iranian oil supplies.

If oil supplies from Iran were cut off, Britain, as the Common Market's only major oil producer, would come under pressure to guarantee a minimun level of supply to its partners and thus deplete its reserves faster than London desires. British officials, always sensitive about outside claims on their oil, reportedly have been reluctant to consider such a sharing plan.