Joan B. Kroc, widow of the McDonald's fast-food magnate, has donated $1 million to the mayor's campaign to attract a monthlong Soviet Arts festival that the city hopes will boost its cultural reputation.

Mayor Maureen O'Connor, who announced the gift Tuesday at a news conference, is scheduled to leave Friday for the Soviet Union to discuss the proposed 1990 event with Soviet officials and to recruit performers."We are well on our way to having a very successful festival, if we can get the Soviet Unionmally accept the donation today, which comes in the form of McDonald's stock and will remain in an interest-bearing account until it is spent, City Attorney John Witt said. The event could cost as much as $4 million.

Kroc, widow of Ray Kroc and owner of the San Diego Padres, said through a spokeswoman, "I am proud to be part of this effort to promote international understanding through cultural exchange."