President Bush said Sunday for the first time that the United States, China and other nations may try to defuse a crisis with North Korea by offering Pyongyang written security assurances in exchange for a commitment to scrap its nuclear weapons program. Bush rejected North Korea’s demand for a formal no-invasion treaty, saying, “That’s off the table.” But he left the door open for a security pledge, agreed to by several countries, that would fall short of an actual treaty. Nuclear tensions hung over Monday’s opening of a 21-nation summit of Asian-Pacific leaders, along with disputes over trade and the U.S. occupation of postwar Iraq. On the economic front, China refused to give ground in a currency argument with Washington. Full Story