British Foreign Secretary Francis Pym, expressing concern that the continuing dispute over the Siberian natural gas pipeline could be a "disaster for the West," travels to the United Nations this weekend, hoping that a meeting can be arranged among the representatives of the United States and the four European countries involved in the pipeline issue.

In a meeting yesterday with American correspondents here, Pym said, "The most urgent thing now for the West is to agree on a framework, a coherent strategy for trade with" the Soviet Bloc.

"Economic sanctions alone," he added, "are not likely to be effective in achieving political change in the Soviet Union or Eastern Europe."

Pym's call for a meeting on the issue with Secretary of State George P. Shultz and envoys from France, Italy and West Germany reflects Britain's eagerness to resolve the differences over supply of equipment for the pipeline that have strained the alliance for months.

But the generalized approach he proposes for such a session indicates that little hope exists for a quick end to the specific problem of Europe's defiance of President Reagan's embargo on supplies and technology for the pipeline or to the American penalties against a number of European companies. Asked whether progress has been made in resolving the matter in recent weeks, a senior British official replied, "not a lot."

After a round of consultations, the Europeans were unable to agree on a strategy for tightening trade and credit terms with the Soviets that could be used to encourage Reagan to relax sanctions on firms that have shipped goods for the pipeline. France has refused to offer what would be seen as concessions to the American position. Moreover, West German policy is severely hampered by the country's political crisis in which Chancellor Helmut Schmidt's coalition has collapsed.

So far Pym has been unable to arrange a meeting at the United Nations earmarked for tackling the pipeline problem even under the guise of a broader discussion of principles. Shultz has indicated that he is ready for such talks, but France has not, sources said. With the envoys in New York, however, Pym appears to feel the chances for some form of discussions will be better.

Shultz is to hold a series of bilaterial meetings with the Europeans at the United Nations starting with French Foreign Minister Claude Cheysson Sunday. Some European officials have also noted that a meeting of NATO foreign ministers the first weekend in October could provide an opportunity to discuss the crisis.

In his remarks yesterday, Pym said that despite the pipeline controversy, he believes the alliance is in "good health" and that the importance of trade with the Soviet Bloc should not be "exaggerated." He also said Britain shares the Reagan administration's "deep concern" about events in Poland.

"But we must make sure that the disaster for the East in Poland doesn't in any sense become a disaster for the West," he said. "In my view, this difference over the pipeline does not affect the fundamental unity of the alliance, but we must resolve it quickly."

Pym's plan, officials explained, is for one meeting to agree on the objectives of Western trade with the Soviet Bloc, followed by sessions in which means could be devised for achieving those goals and in the process resolve the pipeline squabble. Given the inability of European countries to agree among themselves and the absence of any sign of compromise from Reagan, sources conceded, a breakthrough next week is a long shot.