Aides were quick to dismiss the incident, which has happened under past presidents hurrying to pressing events. "It was just momentary," said spokesman Mike Hammer, who explained that Clinton always has an aide with the nuclear codes close by and that the requirement that he was within "the time frame factor was not an issue." Clinton hosted the biggestcontingent of foreign leaders in US history with his 50th NATO birthday bash for 44 heads of state and government. Some 900 guests gathered in tents on the mansion's sweeping South lawn, where they were serenaded by opera stars.