The UAE has been a significant U.S. partner in Gulf security for more than two decades, and the alliance is extending to the U.S.-led effort against the Islamic State organization. A 1994 U.S.-UAE defense cooperation agreement (DCA) provides for U.S. military use of several UAE facilities, and about 5,000 U.S. military personnel are in the UAE at those facilities. The UAE was the first Gulf state to order the most sophisticated missile defense system sold by the United States, demonstrating support for U.S. efforts to assemble a regional missile defense network against Iran. The UAE has helped pressure Iran by implementing financial and economic sanctions against it, while avoiding antagonizing that large neighbor by maintaining trade and commercial ties with it. The UAE has sought to use a relaxation of tensions produced by ongoing nuclear negotiations between Iran and the international community to try to resolve a territorial dispute with Iran. Yet, suggesting continued wariness of Iranian ambitions in the Gulf, the UAE has sought U.S. assurances that the United States will maintain its commitment to Gulf security.