Debate in the US Senate began today on the Comprehensive Test Ban Treaty (CTBT) scheduled for a vote on Tuesday. The treaty would ban not only atmospheric testing, but also underground testing for the nations that sign and ratify it. Currently, with Senate Republicans united in their opposition, the treaty is far short of the 67 votes needed for passage. As a result, the White House and leading senate Democrats are seeking to delay the vote rather than have the treaty go down to defeat. Internationally, the treaty is still far short of sufficient support to be put into effect, needing ratification in another 21 countries before it would be considered binding. Despite the strong Senate opposition to ratification, the United States has actually observed the terms of the treaty since 1992. The sites listed provide information about the test ban treaty and the debate.