The United States gave China a six-month reprieve from Iran financial sanctions on Thursday, avoiding a diplomatic spat with a country whose support it needs to try to quell violence in Syria and rein in Tehran's nuclear ambitions. With Thursday's decision to grant exceptions to China, which buys up to a fifth of Iran's oil exports, and Singapore, which buys Iranian fuel oil, the Obama administration has now spared all 20 of Iran's major oil buyers from its unilateral sanctions. The sanctions themselves are designed to pressure Iran to curb its nuclear program, which the West believes aims to develop...