Iran-Contra prosecutors have asked the Supreme Court to reinstate the convictions of Oliver North, a Marine lieutenant colonel who was a key figure in the worst scandal of Ronald Reagan's presidency.

Unless North's convictions are reinstated, the power of Congress to investigate nationally important scandals will be diluted, prosecutors told the high court.North, who later retired from the Marine Corps, was convicted of three felonies on May 4, 1989; he was acquitted of nine other charges. He was ordered to perform 1,200 hours of community service.

North began the community service work in an inner-city drug project, but on July 20, 1990, a split three-judge federal appeals panel threw out his convictions.

The appeals court ruled that some trial witnesses had been exposed to North's nationally televised testimony to Congress, given in July 1987.