A timeline on nuclear weapons development in North Korea:
—1993: North Korea shocks the world by quitting the Nuclear Nonproliferation Treaty amid suspicions that it is developing nuclear weapons.
—1994: North Korea and U.S. sign nuclear agreement in Geneva. North Korea pledges to freeze and eventually dismantle its nuclear weapons program in exchange for international aid to build two power-producing nuclear reactors.
—Aug. 31, 1998: North Korea fires a multistage rocket that flies over Japan and lands in the Pacific Ocean, proving the Koreans can strike any part of Japan's territory.
—Nov. 17: The United States and North Korea hold the first round of high-level talks in Pyongyang over North Korea's suspected construction of an underground nuclear facility. The United States demands inspections.
—Feb. 27-March 16, 1999: During a fourth round of talks, North Korea allows U.S. access to the site in exchange for promises of food. U.S. inspectors find no evidence of any nuclear activity during visit to site in May.
—May 25-28: Former Defense Secretary William Perry visits North Korea and delivers a U.S. disarmament proposal during four days of talks.
—Sept. 13: North Korea pledges to freeze testing of long-range missiles for the duration of negotiations to improve relations.
—Sept. 17: President Clinton agrees to the first significant easing of economic sanctions against North Korea since the Korean War ended in 1953.
—December: A U.S.-led international consortium signs a $4.6 billion contract to build two nuclear reactors in North Korea.
—July 2000: North Korea renews its threat to restart its nuclear program if Washington does not compensate for the loss of electricity caused by delays in building nuclear power plants.
—June 2001: North Korea warns it will reconsider its moratorium on missile tests if the Bush administration doesn't resume contacts aimed at normalizing relations.
—July: State Department reports North Korea is going ahead with development of its long-range missile. A senior Bush administration official says North Korea has conducted an engine test of the Taepodong-1 missile.
—December: President Bush warns Iraq and North Korea that they would be "held accountable" if they developed weapons of mass destruction "that will be used to terrorize nations."
—Jan. 29, 2002: Bush labels North Korea, Iran and Iraq an "axis of evil" in his State of the Union address. "By seeking weapons of mass destruction, these regimes pose a grave and growing danger," he says.
—April 6: North Korea agrees to revive stalled dialogue with Washington and South Korea and is willing to hold talks with an American envoy.
—Aug. 14: South and North Korea agree to hold family reunions and resume contacts on a range of issues, signaling the resumption of their reconciliation process after months of tension.
—Sept. 25: President Bush plans to send an envoy to North Korea, reopening security talks with the country for the first time in almost two years.
—Oct. 4: North Korean officials tell visiting U.S. delegation that the country has a covert nuclear weapons program in violation of the 1994 agreement.
—Oct. 7: A senior Pentagon official presses the North Korean military for access to four Americans who defected from the U.S. Army in the 1960s and are living in Pyongyang.
—Oct. 13: North Korea warns that the United States' "hostile policy" toward the country was hurting efforts to recover the remains of U.S. soldiers missing from the 1950-53 Korean War.
—Oct. 16: U.S. officials publicly reveal discovery of North Korea's nuclear weapons program.