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(CNN) -- Below is a chronology of the development of North Korea's nuclear weapons program.
Five nations -- the United States, South Korea, Russia, China and Japan -- are applying pressure on Pyongyang to get the secretive nation to give up its nuclear weapons ambitions.
North Korea says it has quit the Nuclear Nonproliferation Treaty amid suspicions that it is developing nuclear weapons. It later reverses that decision.
North Korea and the United States sign an agreement where Pyongyang pledges to freeze and eventually dismantle its nuclear weapons program in exchange for international aid to build two power-producing nuclear reactors.
August: North Korea fires a multistage missile over Japan and into the Pacific Ocean, proving it can strike any part of Japan's territory.
November: 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.
May: Former Defense Secretary William Perry visits North Korea and delivers a U.S. disarmament proposal.
September 17: President Bill Clinton eases economic sanctions against North Korea.
September 13: North Korea pledges to freeze long-range missile tests.
December: A U.S.-led consortium signs a $4.6 billion contract for two Western-developed light-water nuclear reactors in North Korea.
July: North Korea threatens to restart its nuclear program if Washington doesn't compensate for the loss of electricity caused by delays in building nuclear power plants.
June: North Korea warns it will reconsider its moratorium on missile tests if the administration of U.S. President George W. Bush doesn't resume contacts aimed at normalizing relations.
July: U.S. State Department reports North Korea is going ahead with development of its long-range missile. A Bush administration official says North Korea conducts an engine test of the Taepodong-1 missile.
December: U.S. 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."
January 29: 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.
October: The Bush administration reveals that Pyongyang had admitted operating a secret nuclear weapons program in violation of the 1994 agreement. North Korean officials acknowledged the program after U.S. officials confronted them with evidence.
November: The United States, Japan and South Korea halt oil supplies to North Korea promised under a 1994 deal.
December: North Korea removes IAEA monitoring seals and cameras from its nuclear facilities and expels the watchdog agency's inspectors.
January 10: North Korea withdraws from the Nuclear Nonproliferation Treaty.
February 5: North Korea's official news agency says the nation has reactivated its nuclear power facilities.
February 12: The 35-member International Atomic Energy Agency (IAEA) board of governors declares North Korea in breach of atomic safeguards and refers the case to the U.N. Security Council.
February 24: North Korea test fires a land-to-ship missile into the sea between the Korean Peninsula and Japan.
February 26: The United States says North Korea has reactivated its five-megawatt nuclear reactor at Yongbyon.
March: North Korea test fires a land-to-sea anti-ship missile into the Sea of Japan.
July: A senior U.S. official says North Korea has begun reprocessing spent nuclear fuel rods, suggesting the communist country intends to produce nuclear weapons.
August: The U.S., North Korea, South Korea, China, Japan and Russia take part in talks about the crisis in North Korea.
February: The six nations hold a second round of talks but report little progress, other than agreement to meet again.
June: The U.S., North Korea, South Korea, China, Japan and Russia take part in a third round of talks.
August: North Korea says it will not attend working meetings to prepare for the proposed six-nation summit scheduled in September. North Korea offers to freeze its nuclear program in exchange for aid, easing of sanctions and being removed from the U.S. list of state sponsors of terrorism. The United States wants North Korea to disclose all nuclear activities and allow inspections.
September: Further proposed six-nation talks are postponed indefinitely as the United States and North Korea blame each other for the impasse.
February: North Korea says it will "bolster its nuclear weapons arsenal," in response to what it says are U.S. efforts to topple its government. It is Pyongyang's first public admission it has nuclear weapons.
March: U.S. Secretary of State Condoleezza Rice says if efforts to persuade North Korea to give up its nuclear weapons program fail, Washington and the international community will pursue "other ways."
Meanwhile the head of the U.N. nuclear watchdog agency, Mohammed ElBaradei, says North Korea poses more of a nuclear threat than Iran because it already has nuclear material that could go into a weapon.
May: North Korea, in a statement identical to one issued two years earlier, says it has finished extracting 8,000 fuel rods from its reactor at Yongbyon, which it shut down a month ago.
June: North Korea says it has a stockpile of nuclear weapons and is building more, even as it discusses a return to six-party talks on its nuclear program.
July: North Korea says it will return to the talks, due to be held in the week of July 25. Pyongyang joins fourth round of six-party talks, saying it is willing to work towards the denuclearization of the Korean peninsula.
August: After meeting for 13 straight days, diplomats from the U.S., the two Koreas, China, Japan and Russia decide to take a recess from talks. Prospects for a deal on scrapping North Korea's nuclear program are uncertain, U.S. negotiator Christopher Hill says. Pyongyang hints at compromise after saying it may be willing to offer proof that it does not have a uranium-based weapons program. Talks are put on hold until September.
September: North Korea and the U.S. remain at odds as talks resume, after Pyongyang reiterates its demands to maintain a civilian nuclear program. North Korea agrees to give up its entire nuclear program, including weapons, in return for aid and security guarantees. Later, North Korea says it will only do so if the U.S. provides a light-water reactor for civilian power. The U.S. and Russia reject Pyongyang's demand.
November: The talks hit an impasse after North Korea is angered by U.S. financial restrictions against banks and North Korean companies for their alleged involvement in currency counterfeiting and other illicit activities.
April: North Korea offers to resume talks if U.S. releases frozen North Korean assets originating from a bank in Macau.
July: North Korea test-fires six missiles, including a long-range Taepodong-2 rocket believed capable of reaching western United States. Taepodong rocket fails after 40 seconds, but U.S. denounces tests as "provocative."
October 9: North Korea's official Korean Central News Agency (KCNA) reports the country has performed a successful underground nuclear test.
October 14: The U.N. Security Council votes unanimously to impose a wide set of sanctions on North Korea as punishment for the Asian nation's claimed nuclear weapons test. North Korea rejects the resolution and walks out of the security council chamber.
January 22: Envoys to the six-party talks on North Korean nuclear disarmament sound rare notes of optimism, raising hopes for progress after their expected return to the bargaining table in coming weeks.
January 27: North Korea expresses outrage at a British newspaper's report that Pyongyang was sharing its nuclear weapons technology with Iran, dismissing it as a "bid to mislead public opinion."
January 31: Pyongyang will feel compelled to announce plans for another nuclear test if a financial dispute with Washington is not resolved, a source says, a sign of Pyongyang's impatience with a lack of progress in talks.
February 13: North Korea agrees to take first steps toward nuclear disarmament and shut down its main reactor within 60 days before eventually dismantling its atomic weapons program after six-party talks in Beijing.
A North Korean soldier scans the border checkpoint with South Korea.
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