Since Congress returned in early September from its summer recess, the Bush Administration had been focused on passing a use-of-force authorization which would allow the President to undertake unilateral military action against Iraq. Progressives opposed the use-of-force resolution because, in their view, military actions against Iraq should be undertaken with strong international support (such was the case in 1991 when the United Nations backed the U.S.-led Iraqi invasion). Moreover, Progressives worried that establishing a doctrine of preemption-in which the U.S. could attack any country determined by the president to be threatening-would undermine international law and serve to isolate the U.S. from the rest of the world. Moreover, Progressives worried that the doctrine of preemption could be used by other countries to justify unilateral military actions. The consolidation of presidential power was also a concern to Progressives. Progressives pointed out that the U.S. Constitution specifies that Congress, and not the President, is the sole entity responsible for declaring war. During debate on the use-of-force resolution, Congresswoman Barbara Lee (D-CA) proposed an amendment which would have urged President Bush to work through the United Nations to ensure that Iraq is not developing weapons of mass destruction. Progressives supported Lee's proposal as a way to insure international cooperation in a potential conflict with Iraq. The Lee amendment was defeated on a 72-355 vote.