Soviet rock star Boris Grebenshchikov was denied permission Friday to travel to the United States to meet top U.S. musicians and discuss joint recordings, according to the company sponsoring the trip. Grebenshchikov was informed that Soviet Minister of Culture Vasily Zakharov intervened to stop the trip temporarily, a spokeswoman for Belka International told the Associated Press. She said Grebenshchikov was told the refusal was for a 10-day period, but was not told the reason for it. Grebenshchikov, 33, is leader of the Leningrad group Aquarium, one of the Soviet Union's most popular bands. He was to have met with James Taylor, Paul Simon and Willie Nelson during his visit, which also included a trip to Los Angeles.