Three panelists speaking at the Kennedy School of Government last night agreed that peace movements in Western Europe pose a serious obstacle to efforts by the United States and other NATO countries in designing and implementing effective nuclear strategies.

Yet the speakers, one the director of a foreign policy research institute in West Germany, another a State Department official, and the third, the director of the Center for European Studies (CES) at Harvard, differed in their interpretation of the influence the peace movements should have on U.S. and NATO arms control policies and other relations with the Soviet Union.

Speaking on what he called the traditional issue of East-West relations. Karl Kaiser, director of the Institute of Foreign Policy Research in Bonn, Germany, said the peace movement threatened NATO's strategy of "flexible response" to any Soviet nuclear threat. He questioned whether NATO governments could in the future design and implement national security strategies without the Soviet Union subtly undermining their public support.

Kaiser described the fierceness of the Reagan administration's anti-Soviet rhetoric as a leading impetus to the growth of the peace movement in Western Europe, saying its power comes mostly from the voice of small, but highly articulate minorities, such as the West German magazine, Der Spiegel.

The challenge facing the United States and NATO countries, he said, must be to preserve the atmosphere of cooperation with the overwhelming majority of people who are more sympathetic to the traditional goal of nuclear deterrence in Europe.

Thomas M.T. Niles, deputy assistant for European Affairs at the State Department, said the Reagan administration's failure to woo the entire populations of Western European countries reflects its inability to manage public opinion effectively. He described a situation where the media in those countries along with Soviet propaganda contributed to the picture of the United States as aggressor and Soviet Union as peacemaker.

In response to the state department official, Stanley Hoffman, director of the CES, said the peace movement poses a problem beyond managing public opinion. He described Europe's disenchantment with the United States as a combination of the remembrance of World War II and the fear of nuclear destruction in Europe. "When people are squeezed in between things they can't really do anything about, they are led to all sorts of fantasies," Hoffman said.

He mentioned the belief among resisters that the Soviets had no bad intentions, and that the United States already had deployed a large enough number of weapons for effective deterrence.

Kaiser summed up his view of the ultimate imperative for the United States: The United States has to negotiate with good faith, and reach an agreement on arms control."