From 1954 to 1979, the United States was a partner with Taiwan in a mutual defense treaty. The United States remains one of the main supporters of Taiwan and, through the Taiwan Relations Act passed in 1979, has continued selling arms and providing military training to the Armed Forces. This situation continues to be an issue for the People's Republic of China, which considers US involvement disruptive to the stability of the region. In January 2010, the US announced its intention to sell $6.4 billion worth of military hardware to Taiwan. As a consequence, the PRC warned that its co-operation with the US on international and regional issues could suffer and that the companies involved, namely Raytheon, Lockheed Martin, Boeing, and United Technologies, could face Chinese sanctions.