美国认为,已有81个国家拥有巡航导弹或具备制造巡航导弹的能力,巡航导弹已对美国构成重大威胁,现有导弹防御系统不足以消除这一威胁。在沙特发生针对美国侨民的恐怖爆炸和国内安全部发出恐怖分子可能实施类似“9·11”袭击的信息后,五角大楼采取动用国家导弹防御系统的措施:在纽约、华盛顿、费城等重要城市周围增加监视领空的值班力量,部署多架预警机实施全天候值 The United States believes that 81 countries already own cruise missiles or have the capability to manufacture cruise missiles, which have posed a major threat to the United States. The existing missile defense system is not sufficient to eliminate this threat. After the terrorist bombing against U.S. nationals in Saudi Arabia and the Department of Internal Security's message that terrorists might launch similar “9/11 attacks”, the Pentagon took the initiative of using the NMD system: in major cities such as New York, Washington and Philadelphia Surrounding the watch air force to increase the watch on the strength of the deployment of multiple early warning aircraft to implement all-weather value