Key dates in the history of nuclear weapons development in North Korea:
North Korea begins operations of a 5-megawatt reactor at Yongbyon built with Soviet help.
1993: North Korea announces it will quit the Nuclear Nonproliferation Treaty, later suspends its withdrawal.
1994: North Korea and the United States sign an agreement in Geneva. The North pledges to freeze - and eventually dismantle - its plutonium-based nuclear weapons programme in exchange for help building two power-producing nuclear reactors.
September 17, 1999: Bill Clinton, the US president, agrees to first major easing of economic sanctions against North Korea since the Korean War's end in 1953.
October 23-24, 2000: Madeleine Albright, the US secretary of state, visits Pyongyang, the highest-ranking US official ever to visit North Korea.
January 29, 2002: George Bush, the US president, labels North Korea, Iran and Iraq an "axis of evil."
October 4, 2002: North Korea tells visiting US delegation it has a uranium enrichment programme, Washington says.
November 11, 2002: US and Asian allies - Japan, South Korea - halt oil supplies to the North promised in the 1994 deal and suspend construction of two new reactors.
January 10, 2003: North Korea says it will withdraw from the Nuclear Nonproliferation Treaty.
August 27-29, 2003: North Korea joins first round of six-nation talks, involving envoys from China, Japan, Russia, the US and South Korea.
February 25-28, 2004: Second round of six-nation talks.
June 23-26, 2004: Third round of six-nation talks.
February 10, 2005: North Korea announces it has nuclear weapons.
July 26, 2005: Fourth round of six-nation talks is held, ending in recess after 13 days with no agreement.
September 13, 2005: Six-nation talks resume.
September 15, 2005: US blacklists Macau-based bank for alleged counterfeiting and money-laundering by North Korea, leading the bank to freeze North Korean assets.
September 19, 2005: North Korea promises to dismantle nuclear programmes in exchange for pledges of energy assistance; US says it has no plans to invade, and will respect North's sovereignty in an agreement ending talks.
November 9-11, 2005: Fifth round of six-nation talks.
January 3, 2006: North Korea says it will not return to talks unless the US lifts financial restrictions imposed in 2005.
July 5, 2006: North Korea launches seven missiles - including a long-range model - into the Sea of Japan, drawing international condemnation and a UN Security Council resolution condemning the act.
October 9, 2006: North Korea says it has conducted its first-ever nuclear test.
October 14, 2006: UN Security Council unanimously adopts a resolution imposing wide-ranging economic and diplomatic sanctions on North Korea for its nuclear test.
December 18-22, 2006: Six nations envoys meet in wake of nuclear test, no breakthrough made.
January 16-18, 2007: US and North Korean envoys meet in Berlin.
February 8-13, 2007: Six-nation talks resume in Beijing, a tentative agreement on disarming Pyongyang is reached. The draft plan contains commitments on disarmament and energy aid along with "initial actions" to be taken by certain deadlines.
July 14, 2007: North Korea says it has shut down the Yongbyon reactor.
September 6, 2007: Israeli plans attack and destroy a site in Syria. After months of speculation the US later says the site was a nuclear reactor under construction with North Korean help, following a design similar to the Yongbyon plant.
November 2007: North Korea begins disabling Yongbyon reactor under surpervision of international - including US - experts.
December 31, 2007: North Korea misses agreed deadline for it to submit a full declaration of all its nuclear activities.
May 2008: North Korea hands US officials more than 18,000 pages of records on the Yongbyon plant. The US later says it will provide 50,000 tons of much-needed food aid to North Korea as a humanitarian gesture.