Harvard University today kicked off a $5 million fund-raising campaign for its Russian Research Center in what officials here called an effort to replace a "lost generation" of Soviet scholars the nation has neglected to train.

In a speech of support here, Arthur A. Hartman, U.S. ambassador to the Soviet Union, said Soviet scholarship in this country has been declining for more than a decade and is now dwarfed by the effort the Soviets invest in understanding America. "You get into a period where things are calmer, and people somehow think there is no need to do anything," Hartman said. "With the billions we spend on defense, we could at least do something for our basic knowledge of these people and their policies."

The Harvard campaign was spurred in part by a $10 million donation last year from W. Averill Harriman, a former ambassador to the Soviet Union, to a rival research center at Columbia University, now known as the W. Averill Harriman Institute for Advanced Study of the Soviet Union.

But Harvard and Columbia officials both said that more than Ivy League rivalry is at stake. Funding for Soviet studies in this country decreased by 70 percent between 1965 and 1985, Hartman said, and the resulting shortfall in Soviet experts compromises U.S. ability to understand its superpower rival.

"When the current generation of Soviet scholars retires, we won't have people who understand how the Soviet Union operates," said Jonathan E. Sanders, assistant director of Columbia's center. "It takes longer to develop a Soviet expert than a sophisticated weapons system."

Marshall I. Goldman, associate director of Harvard's center, said there are more English-language teachers in the Soviet Union than Russian-language students in the United States. There are 7,500 specialists on America in the Soviet Union, according to an aide to Sen. Richard G. Lugar (R-Ind.), while about 200 Americans each year complete doctoral studies in some Soviet-related field.