President Reagan's announcement yesterday of a U.S.-European "plan of action" on East-West trade is being portrayed in Western Europe as no breakthrough but simply a reinforcement of previous alliance understandings.

While allied officials welcomed the removal of American sanctions against the Soviet gas pipeline, British Foreign Minister Francis Pym declared today that European governments had made "no concessions" in return for what he said had been "a unilateral decision by the Americans." Strategic studies on various aspects of East-West trade that the allies have agreed to undertake would be done, Pym said, "without commitments" to impose new limits.

Other officials said privately that the alliance accord constituted a promise only to pursue more intensively a program of review and consultation on trade relations with the Soviet Bloc that Western leaders already had outlined at summit meetings last June in Versailles and Bonn.

Disputes arose after those summits as to just how much restraint in Soviet Bloc business the allies had endorsed. The sharpest interpretative clash occurred between Washington and Paris, and this conflict appeared still somewhat unresolved this weekend in view of France's declaration that it was not a party to the new agreement.

At best, the latest accord seems to represent a reaffirmation by the Western Europeans that trade is at least an element worth considering in the overall East-West strategy mix, in the view of observers here. But it is still uncertain whether the North Atlantic Treaty Organization governments, plus Japan, can work out new restrictions on economic relations with the Soviet Bloc.

"A conceptual framework already existed in NATO that will now be reexamined and will become more precise," explained a senior West German official involved in drafting the agreement. "We have essentially made more precise how, in the framework we already agreed to, more headway can perhaps be made."

At the same time, this official and other European diplomats stressed that any new concrete limits in the three key economic areas slated for review -- financial credits, technology transfer and energy -- are bound to involve lengthy U.S.-European negotiations in specialized diplomatic forums.

"If we reach agreement at the end of the studies, that would be helpful," Pym told a British Broadcasting Corp. radio interviewer. He said misunderstandings about what had been achieved at the Versailles economic summit had led to the damaging extension of U.S. sanctions against the Soviet pipeline project. "We will try to assure that nothing like it happens again," he said.

Some of what is in the new agreement reflects intensified efforts already under way. In the area of technology transfer, for instance, alliance officials have been meeting for months on a U.S. request to add scores of industrially sensitive items to a list of strategic goods prohibited for sale to the Soviet Bloc. The American aim is to restrict not only individual products, such as computers, but also basic technologies, such as microcircuitry, that could have a military application in the Soviet Union.

Officials involved in these secretive discussions say a study on expansion of the existing embargo list could take as long as a year.

In the area of financial credits, European officials pointed to recent new costs imposed on Soviet loans and indicated a reluctance to add more.

Following last summer's summit agreements, Western states increased the minimum interest rate on government-subsidized loans to Moscow by about 4 percent more than last year to 12.4 percent.

Under the new accord, Western governments have accepted procedures to share more extensively the details of their individual financial relations with the Soviets. Officials here say the procedures were agreed to in principle at Versailles. But U.S. attempts to get the allies to insist on larger down payments, shorter payback periods and other new conditions for Soviet loans continue to be looked on hesitantly here. At the same time, such options are seen by officials as more acceptable than hard limits on credit volumes.

European officials made clear they still do not back the notion that economic measures could or should be used to punish the Soviet Union. "It is important to understand what we are talking about," said another high-ranking West German official. "We are not talking about a trade war or about punishing others, but how to serve our own security interests."

In Moscow, the official news agency Tass, in what appeared to be the first Soviet reaction to Reagan's announcement, said Sunday that the U.S. trade sanctions had been a failure, The Associated Press reported. "By means of those measures, Washington unsuccessfully tried to frustrate the construction of the Siberia-Western Europe gas pipeline," Tass said.