Humphries, a world-champion bobsledder, won three Olympic medals for Canada last decade. After defecting over alleged abuse, she needed U.S. citizenship to be able to compete in Beijing.
King won bronze in the 100m at the first world championships in 1983.
Experts say IOC president Thomas Bach's call with Peng Shuai is more propaganda than evidence of Peng's safety.
A diplomatic boycott would not affect Olympic athletes from the United States.