Commerce Secretary Robert A. Mosbacher is leading 15 top American business executives on a mission to Moscow next week to advise the Soviets on bolstering their sagging economy and suggest ways they can increase their oil production.

On the trip will be the chief executives of major U.S. oil companies, who will offer advice on how to turn around the continued decline in Soviet oil production and seek business for themselves as Moscow opens more of its petroleum resources for development by foreign companies.

Oil is the major source of hard currency for the Soviet Union, and Moscow is seeking increased production to give its economy a needed boost, Mosbacher said. While the Soviet Union is the world's largest producer of oil, with one-sixth of the global supply coming from its wells, its output has been falling steadily because of mismanagement, outdated equipment and inefficient pipelines.

An increase of oil production would not only help the Soviet economy but also relieve Western Europe's dependence on the Middle East for its energy supplies.

"We hope to help them turn around their dropping {oil-production} rate," Mosbacher said yesterday.

A former Texas oil wildcatter, Mosbacher said new methods and technologies available in the United States could help Moscow squeeze more oil out of its present fields and find new ones. The Soviets have indicated a willingness to open fields to exploration and production by Western companies and already have signed exploration agreements with Chevron Corp. and Texaco Inc. Chief executives from both companies are on the trip. Moscow invited Western oil companies this week to bid for exploration and production rights in two regions covering 90,000 square miles.

The Mosbacher trip comes at a time of thaw in U.S.-Soviet relations, with Moscow joining the United States in criticizing Iraq, its former Middle East ally, for invading Kuwait. As a result of that cooperation, White House spokesman Marlin Fitzwater announced Wednesday that the United States is rethinking its opposition to direct economic aid to the Soviets.

Bush and Gorbachev will meet in Finland on Sunday in a hastily called summit meeting. Immediately afterward, Bush will brief Mosbacher and the business executives, who will stop in Helsinki on their way to Moscow.

While the Mosbacher business development trip was set before Iraq's Aug. 2 invasion of Kuwait, the political and economic fallout is expected to play a role in the talks, especially in the extra emphasis given to improving Soviet oil production.

Executives on the trip represent industry sectors other than oil that Gorbachev and his aides have identified as priorities for improving the Soviet economy. These include farming, transportation and housing.