The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) PrepCom's international monitoring system detected data indicating that North Korea had conducted a nuclear test on January 6, 2016. The CT BTO PrepCom held a symposium for experts called Science and Diplomacy for Peace and Security in January 2016. The spring CTBTO PrepCom meeting was a "20 Year Ministerial" from June 13-14, 2016, to mark the 20 th anniversary of the opening for signature of the Comprehensive Nuclear-Test-Ban Treaty ( CTBT ) and to explore options for advancing its entry into force. At that meeting, Pakistan reiterated its stance that "it will not be the first in its region to resume nuclear testing." On August 29, 2016, the CTBTO PrepCom held an international conference—On the International Day Against Nuclear Testing—in Almaty, Kazakhstan, to mark 25 years after the nuclear test site in Kazakhstan was closed down. The United States is working with other countries to draft a UN Security Council Resolution marking the 20 th year after the signing of the CTBT on September 24. The CTBTO PrepCom will meet in November 2016. While the CTBT was opened for signature in 1996, it has not entered into force, leaving a ban on nuclear testing as the oldest item on the arms control agenda. Efforts to curtail tests have been made since the 1940s. In the 1950s, the United States and Soviet Union conducted hundreds of hydrogen bomb tests. The radioactive fallout from these tests spurred worldwide protest. These pressures, plus a desire to improve U.S.-Soviet relations in the wake of the Cuban Missile Crisis of 1962, led to the Limited Test Ban Treaty of 1963, which banned nuclear explosions in the atmosphere, in space, and under water. The Threshold Test Ban Treaty, signed in 1974, banned underground nuclear weapons tests having an explosive force of more than 150 kilotons, the equivalent of 150,000 tons of TNT, 10 times the force of the Hiroshima bomb. The Peaceful Nuclear Explosions Treaty, signed in 1976, extended the 150-kiloton limit to nuclear explosions for peaceful purposes. President Carter did not pursue ratification of these treaties, preferring to negotiate a comprehensive test ban treaty, or CTBT, a ban on all nuclear explosions. When agreement on a CTBT seemed near, however, he pulled back, bowing to arguments that continued testing was needed to maintain reliability of existing weapons, to develop new weapons, and for other purposes. President Reagan raised concerns about U.S. ability to monitor the two unratified treaties and late in his term started negotiations on new verification protocols. These two treaties were ratified in 1990. With the end of the Cold War, the need for improved warheads dropped and pressures for a CTBT grew. The U.S.S.R. and France began nuclear test moratoria in October 1990 and April 1992, respectively. In early 1992, many in Congress favored a one-year test moratorium. The effort led to the Hatfield-Exon-Mitchell amendment to the FY1993 Energy and Water Development Appropriations Bill, which banned testing before July 1, 1993, set conditions on a resumption of testing, banned testing after September 1996 unless another nation tested, and required the President to report to Congress annually on a plan to achieve a CTBT by September 30, 1996. President George H. W. Bush signed the bill into law ( P.L. 102-377 ) October 2, 1992. The CTBT was negotiated in the Conference on Disarmament. It was adopted by the U.N. General Assembly on September 10, 1996, and was opened for signature on September 24, 1996. As of August 2016, 183 states had signed it and 164 had ratified. United States: As of August 2016, the United States had signed but not ratified the CTBT. The following history casts light on the U.S. position. Under the Hatfield-Exon-Mitchell amendment, President Clinton had to decide whether to ask Congress to resume testing. On July 3, 1993, he said, "A test ban can strengthen our efforts worldwide to halt the spread of nuclear technology in weapons," and "the nuclear weapons in the United States arsenal are safe and reliable." While testing offered advantages for safety, reliability, and test ban readiness, "the price we would pay in conducting those tests now by undercutting our own nonproliferation goals and ensuring that other nations would resume testing outweighs these benefits." Therefore, he (1) extended the moratorium at least through September 1994; (2) called on other nations to extend their moratoria; (3) said he would direct DOE to "prepare to conduct additional tests while seeking approval to do so from Congress" if another nation tested; (4) promised to "explore other means of maintaining our confidence in the safety, the reliability and the performance of our own weapons"; and (5) pledged to refocus the nuclear weapons laboratories toward technology for nuclear nonproliferation and arms control verification. He extended the moratorium twice more; on January 30, 1995, the Administration announced his decision to extend the moratorium until a CTBT entered into force, assuming it was signed by September 30, 1996. On September 22, 1997, President Clinton submitted the CTBT to the Senate. He asked the Senate to approve it in his State of the Union addresses of 1998 and 1999. Senate Foreign Relations Committee Chairman Helms rejected that request, saying that the treaty "from a non-proliferation standpoint, is scarcely more than a sham" and had low priority for the committee. In summer 1999, Senate Democrats pressed Senators Helms and Lott to permit consideration of the treaty. On September 30, 1999, Senator Lott offered a unanimous-consent request to discharge the Senate Foreign Relations Committee from considering the treaty and to have debate and a vote. The request, as modified, was agreed to. The Senate Armed Services Committee held hearings October 5-7; the Foreign Relations Committee held a hearing October 7. It quickly became clear that the treaty was far short of the votes for approval, leading many on both sides to seek to delay a vote. As the vote was scheduled by unanimous consent, and several Senators opposed a delay, the vote was held October 13, rejecting the treaty, 48 for, 51 against, and 1 present. At the end of the 106 th Congress, pursuant to Senate Rule XXX, paragraph 2, the treaty moved to the Senate Foreign Relations Committee calendar, where it currently resides. The Bush Administration's Nuclear Posture Review and Nuclear Testing: In the FY2001 National Defense Authorization Act ( P.L. 106-398 , §1041), Congress directed the Secretary of Defense, in consultation with the Secretary of Energy, to review nuclear policy, strategy, arms control objectives, and the forces, stockpile, and nuclear weapons complex needed to implement U.S. strategy. Although the resulting Nuclear Posture Review is classified, J.D. Crouch, Assistant Secretary of Defense for International Security Policy, presented an unclassified briefing on it on January 9, 2002, dealing in part with the CTBT and nuclear testing. He stated there would be "no change in the Administration's policy at this point on nuclear testing. We continue to oppose CTBT ratification. We also continue to adhere to a testing moratorium." Further, "DOE is planning on accelerating its test-readiness program" to reduce the time needed between a decision to test and the conduct of a test, which was then 24 to 36 months. He discussed new weapons. "At this point, there are no recommendations in the report about developing new nuclear weapons ... we are trying to look at a number of initiatives. One would be to modify an existing weapon, to give it greater capability against ... hard targets and deeply-buried targets. And we're also looking at non-nuclear ways that we might be able to deal with those problems." A Washington Post article of January 10, 2002, quoted White House Press Secretary Ari Fleischer as saying that the President has not ruled out testing "to make sure the stockpile, particularly as it is reduced, is reliable and safe. So he has not ruled out testing in the future, but there are no plans to do so." Critics expressed concern about the implications of these policies for testing and new weapons. Physicians for Social Responsibility argued, "The Administration's plan ... would streamline our nuclear arsenal into a war-fighting force, seek the opportunity to design and build new nuclear weapons, and abandon a ten-year-old moratorium on nuclear weapons testing." Another critic felt that increased funding for test readiness would in effect give prior approval for testing. In July 2002 a National Academy of Sciences panel report on technical aspects of the CTBT concluded, in the words of a press release, "that verification capabilities for the treaty are better than generally supposed, U.S. adversaries could not significantly advance their nuclear weapons capabilities through tests below the threshold of detection, and the United States has the technical capabilities to maintain confidence in the safety and reliability of its existing weapons stockpile without periodic nuclear tests." A U.N. draft document of August 5, 2005, for signature by heads of government and heads of state at the U.N. General Assembly meeting of September 2005, contained a provision that the signers "resolve to ... [m]aintain a moratorium on nuclear test explosions pending the entry into force of the Comprehensive Nuclear-Test-Ban Treaty and call upon all States to sign and ratify the Treaty." John Bolton, the U.S. Ambassador to the United Nations, reportedly called for major changes to the draft; the CTBT passage was one of many drawing his objection.