Japan and the United States signed an agreement Friday to expand their cooperation on a joint ballistic missile defense shield, the Japanese Foreign Ministry announced. The pact, signed by Foreign Minister Taro Aso and U.S. Ambassador Thomas Schieffer, commits them to joint production of missiles to intercept incoming missiles, the ministry said in a statement. The agreement had been previously negotiated and was not triggered by the current fears that North Korea is preparing to test a long-range missile. There has been speculation that the United States could try to intercept the missile if it is fired.