WASHINGTON- Over the years, the U.S. government has tried just about everything with North Korea - the threat of war, the cold shoulder, sanctions, lifting sanctions and billions of dollars in aid - to dissuade it from pursuing various arms programs. So what will it do now that the hardline communist regime has admitted to secretly developing nuclear weapons? The possibilities range from diplomatic pressure to more incentives to military action. But the Bush administration was keeping its options open Thursday, revealing little about how it will respond to the unpredictable, longtime adversary. Asked whether the United States might use...