The nuclear issue on the Korean Peninsula began in the early 1990s. The following is a chronology of key events surrounding the issue since 1991:

1991:

Dec. 31 -- The Democratic People's Republic of Korea (DPRK) and South Korea sign a joint declaration on denuclearization of the Korean Peninsula.

1992:

Jan. 30 -- The DPRK and the International Atomic Energy Agency (IAEA) sign comprehensive safeguards agreement in Vienna.

Feb. 19 -- In the sixth round of inter-Korean talks, the prime ministers of the DPRK and South Korea respectively read out an agreement on reconciliation, non-aggression, exchanges and cooperation, and a joint declaration on the denuclearization of the Korean Peninsula. The two documents were approved by DPRK leader Kim Il-sung and South Korean President Roh Tae-woo.

1993:

March 12 -- The DPRK announces that it would withdraw from the nuclear Non-Proliferation Treaty (NPT) in three months, citing the continuance by South Korea and the United States of their "Team Spirit" joint military maneuvers and the IAEA's demand that the DPRK's military facilities be subject to inspection. The DPRK joined the NPT in late 1985.

June 2-11 -- The DPRK and the United States hold formal talks for the first time in New York. In a joint statement issued at the end of the fourth round of talks, the two sides agree on assurances against the threat and use of force, including nuclear weapons, on peace and security in a nuclear-free Korean Peninsula, including impartial application of full-scope safeguards, mutual respect for each other's sovereignty, and non-interference in each other's internal affairs, and on support for the peaceful reunification on the Korean Peninsula. The DPRK announces the suspension of its withdrawal from the NPT.

July 14-19 -- The DPRK and the United States hold their second formal talks in Geneva. The DPRK agrees to have dialogues with the IAEA as soon as possible and the United States says it would help the DPRK reconstruct its nuclear reactors.

1994:

July 8-Aug. 12 -- The DPRK and the United States hold their third formal talks in Geneva. In a joint statement the DPRK agrees to replace the existing graphite-moderated nuclear reactors with light-water reactors. The United States promises to provide a light-water reactor and alternative energy to the DPRK.

Oct. 21 -- The DPRK and the United States sign Framework Agreement in Geneva. Under the accord, the DPRK agrees to freeze its existing nuclear program in exchange for the construction of one 2,000-megawatt light-water reactor or two 1,000-megawatt ones by the United States within 10 years. Before the completion of the light-water project, the United States and other countries would provide heavy oil to the DPRK for energy compensation.

2002:

Oct. 3 -- US presidential special envoy James Kelly visits the DPRK.

Oct. 7 -- A DPRK Foreign Ministry spokesperson says that during his visit Kelly raised "issues of concern" that include "missile production and sales, nuclear program, conventional armed forces, and human rights record" to exert pressure on Pyongyang.

Oct. 20 -- US Secretary of State Colin Powell says the DPRK admitted to Kelly its nuclear program and "blamed us for their actions." The Bush administration considers the 1994 nuclear accord between the United States and the DPRK effectively dead.

Nov. 14 -- Executive members of the Korean Peninsula Energy Development Organization (KEDO), an international consortium administering the 1994 nuclear agreement with the DPRK, meet in New York and decide to suspend fuel oil shipments to the DPRK as of December.

Nov. 29 -- The IAEA Board of Governors adopts a resolution that requires the DPRK to give up its nuclear program, disclose all related facilities and accept IAEA inspections. The resolution also requires the DPRK to provide before March 2003 files on DPRK's position on nuclear program so that the IAEA could decide further actions.

Dec. 22 -- The DPRK declares that it has "started the work of removing the seals and monitoring cameras from the frozen nuclear facilities for their normal operation to produce electricity."

2003:

Jan. 10 -- DPRK Ambassador to the United Nations Pak Gil Yon says that the IAEA and the nuclear Non-Proliferation Treaty (NPT) have become tools of the United States against the DPRK. As a result, the DPRK decides to withdraw from the treaty.

Jan. 25 -- DPRK Foreign Ministry declares that the DPRK is against any move to internationalize the nuclear issue on the Korean Peninsula and urges the United States to talk directly with the DPRK.

Feb. 12 -- The IAEA decides to refer the nuclear issue of the DPRK to the UN Security Council.

April 23-25 -- Thanks to efforts by China and the international community, China, the DPRK and the United States hold three-way talks in Beijing on the nuclear issue on the Korean Peninsula.

Aug. 1 -- The DPRK tells the ROK that it accepts multilateral talks to resolve the nuclear issue. It also says Pyongyang agrees to attend the talks without "adding any important pre-conditions."

Aug. 27-29 -- The first round of the six-party talks, which are held in Beijing from Aug. 27 to Aug. 29 between China, the DPRK, the United States, Russia, the ROK and Japan. The talks end without a clear breakthrough.

Aug. 30 -- The DPRK says the United States shows no intention at the six-party talks to improve ties with and shift policies toward Pyongyang; instead, Washington wants to render it a venue for disarming the DPRK.

Sept. 30 -- The DPRK says it will maintain and even enhance its nuclear deterrent force unless the United States drops its hostile policy toward the country.

Oct. 30 -- China and the DPRK agree in principle to continue the six-party talks on the Korean nuclear issue. The DPRK side stresses that the United States should accept a package solution on the principle of simultaneous actions.

Nov. 5 -- US Secretary of State Colin Powell praises China for hosting and fully participating in the six-party talks over the nuclear issue of the Korean Peninsula, saying China "continues to play an important role" on that issue.

Nov. 16 -- The DPRK says it will maintain the invariable stand to seek a negotiated peaceful solution to the nuclear issue, as well as to take into consideration "written assurances of non-aggression" to which US President George W. Bush referred and to modify the phraseology of the principle of simultaneous actions.

It also declares that the DPRK is ready to abandon in practice its nuclear program under certain conditions.

Dec. 11 -- The DPRK says Pyongyang has to maintain its nuclear deterrents facing Washington's certain activities, confirming that it would not freeze the nuclear activities unconditionally.

It reiterates the demand that in exchange for the freezing of its nuclear activities, Washington must remove the DPRK from the list of nations promoting terrorism, lift the political, economic and military blockades.

2004:

Jan.21 -- An American nuclear weapons expert who joined an unofficial US delegation visiting a nuclear facility at Yongbyon in DPRK said he saw no convincing evidence that the DPRK has the ability to build a plutonium-based nuclear device, though he did see evidence it most likely can make plutonium.

Feb.6 -- Abdul Qadeer Khan, founder of Pakistan's nuclear weapons program, admitted to having transferred nuclear technology secrets to the DPRK.

Feb.21 -- Korean Central News Agency refutes allegations that Pakistan transferred nuclear technology secrets to DPRK, saying the DPRK possesses a self-reliant nuclear deterrent force.

Feb.25-28 -- The second round of six-party talks was held in Beijing. The six parties agreed to set up a working group mechanism for the talks. They also agreed to continue a third round of talks in Beijing in June.

June 23-26 -- The third round of six-party talks was held in Beijing.

Due to differences between the DPRK and the United States, the talks were broken down for more than a year.