CORNING, N.Y. (AP) _ Corning Inc. announced today a long-term supply agreement for optical fiber with several Russian cable manufacturers and Russia's leading cable organization.

The company is the first optical fiber manufacturer to establish such an agreement in Russia. The cable will be used to construct a civilian telecommunications base to provide telephone services to Russian citizens.

The agreement, which will last into the 21st century, must first be approved by the U.S. Department of Commerce.

''Although Russia is still reorganizing, we are trusting that our commitment to Russia's future is a long-term alliance which capitalizes on Corning's strengths in developing partnerships in the global marketplace,'' said Robert Forrest, senior vice president and general manager of the Telecommunications Products Division of Corning.

Under the pact, the All Russian Scientific Institute of the Cable Industry and four Russian cable manufacturers will purchase Corning optical fiber for use in making fiber-optic cable, Corning announced in a statement.

''This agreement allows Corning to contribute to the deployment of advanced optical fiber in a country that now has very little optical fiber in its civilian network,'' Forrest said.

The All Russian Scientific Institute is a government and industry association that represents the majority of the established cable manufacturers in Russia. The cable-making companies associated with the agreement, and represented by the Institute, are located in Moscow and St. Petersburg and also in the towns of Podolsk and Mytishi.

The companies have also agreed to explore the possibility of manufacturing optical fiber in Russia using Corning's patented technology.

Optical fiber, or hair-thin strands of glass, has thousands of times more capacity to carry information over longer distances, at higher speeds and with better quality than copper wire.

Corning, a ceramics, laboratory services and optical fiber company in south central New York, reported $335.7 million in net income for 1992.