For more than a decade Pakistan's determination to have the capacity to build nuclear bombs has strained relations with the U.S. That issue returned to the surface last week, threatening to undermine vital areas of cooperation between Washington and its most important strategic ally in South Asia. U.S. Under Secretary of State for Political Affairs Michael Armacost arrived in Islamabad with a tough message: Pakistan must submit to on-site inspection of its burgeoning nuclear facilities or risk the suspension of a $540 million military- and economic-aid package. The government of President Mohammed Zia ul-Haq firmly rejected the demand.
In public, at...