CASA agencies provide combatant commanders and the service component or subordinate commands with the means to receive and provide mutual logistical support during training and travel, military exercises and operations, or to provide expedited access to the logistical resources of the armed forces of foreign countries to meet the logistical support needs of deployed U.S. forces. The Cross-Acquisition and Services Agreement (ACSA) is negotiated on a bilateral basis between the United States and its NATO allies or coalition partners, allowing U.S. forces to exchange the most common types of support, including food, fuel, transportation, ammunition, and equipment. The agreement in no way obliges a country to take military action. ACSA also exists between third countries. Japan and South Korea have formed ACSAs with countries other than the United States. [1] As of December 18, 2014, the United States had ACSA with 102 countries, with an additional 78 countries eligible for ACSA[2], including most NATO countries, as well as the NATO Support and Supply Agency (NSPA), NATO`s Allied Command Transformation, and the Supreme Headquarters of the Allied Powers Europe (SHAPE). CASA reduces logistics overhead and is considered an important logistical requirement by providing increased interoperability, better operational readiness and cost-effective joint support to field commanders. ACSA achieves this by introducing a mechanism to provide logistics deliveries between two parties for reimbursement in cash, compensation in kind or equivalent exchanges. The Status of the Cross-Acquisition and Service Agreement (ACSA) (formerly known as the NATO Mutual Support Act) was enacted to facilitate the exchange of logistical support, supplies and services between the United States and other NATO forces. It was amended in 1987[3] to allow CASA with the governments of eligible non-NATO countries, with further changes in 1989 and 1990.

It also requires equivalent exchanges (EVEs) of logistical support, supplies and services and allows ACSA with United Nations agencies and approval of the loan or rental of equipment. Annual reports are required that list all CASA transactions in the previous fiscal year and set out requirements for the next fiscal year. .