Serious differences on crucial issues threaten to ignite tensions between the powers.
China vociferously opposes the deal.
University researcher Gao Zhan, right, a permanent U.S. resident whose son and husband are citizens, was arrested for espionage last week after being held for more than a month. Li Shaomin, a U.S. citizen and Hong Kong professor, was taken into custody while visiting the mainland last month. China also fears the U.S. will use a theater missile defense to shield Taiwan from its short-range missiles. Beijing has warned Bush that he risks a new arms race. U.S. and U.N. observers have condemned the crackdown on the Falun Gong spiritual movement.