During the 1970s and 1980s, he was invited to visit the United States on several occasions, meeting with U.S. Presidents Richard Nixon, Ronald Reagan and George H. W. Bush. Following the dissolution of the Soviet Union U.S. relations with Mobutu cooled, as he was no longer deemed necessary as a Cold War ally. Opponents within Zaire stepped up demands for reform. This atmosphere contributed to Mobutu's declaring the Third Republic in 1990, whose constitution was supposed to pave the way for democratic reform. The reforms turned out to be largely cosmetic. Mobutu continued in power until armed forces forced him to flee in 1997. "From 1990 to 1993, the United States facilitated Mobutu's attempts to hijack political change", one academic wrote, and "also assisted the rebellion of Laurent-Desire Kabila that overthrew the Mobutu regime."