Missile Defense Shield Tests Halted: Pentagon officials have canceled several tests of its developing ballistic missile defense shield to avoid "bumping up" against the 1972 Anti-Ballistic Missile Treaty, Defense Secretary Donald Rumsfeld said Thursday. "We have said that we will not violate the [ABM] treaty while it is in force," Rumsfeld said. "It is possible that someone could raise an issue because of ambiguities [the tests raise in light of the treaty’s principals], and we do not want to get into that debate."