c. China
By 1972, China, the United States, and the Soviet Union were each worried about the prospects of closer ties between the other two. Soviet premier Leonid Brezhnev responded to Nixon's China trip by inviting the president to Moscow, where the two leaders signed an arms limitation treaty, SALT |. Both sides agreed not to deploy any nuclear missiles exceeding existing levels and pledged further arms reduction talks. Nixon failed, however, to leverage this new relationship to end the Vietnam War.