The following is a chronology of key events concerning the DPRK's nuclear program:

Dec. 1985 - The DPRK joins the Nuclear Non-proliferation Treaty (NPT), and adheres to a safeguards agreement with the International Atomic Energy Agency (IAEA) on condition that the United States removes nuclear weapons from South Korea.

Sept. 1991 - Then president of the United States, George Bush, announces withdrawal of all US tactical nuclear weapons deployed abroad, including about 100 based in South Korea.

Dec. 1991 - The South-North Joint Declaration on the Denuclearization of the Korean Peninsula is signed. Both sides pledge not to test, produce, receive, store, deploy or use nuclear weapons, and agree to mutual inspections.

Jan. 1992 - The DPRK concludes a comprehensive safeguards agreement with the IAEA and ratifies the agreement in April.

May 1992 - The DPRK declares seven sites and some plutonium to be subject to IAEA inspection.

March 1993 - Facing demands for special inspections, the DPRK announces its intention to withdraw from the NPT in three months.

June 1993 - The DPRK suspends its decision to quit the NPT and agrees to accept IAEA safeguards, after holding talks with the United States.

March 1994 - IAEA inspectors arrive in the DPRK for the first inspections within one year. The DPRK refuses to accept inspections at a plutonium reprocessing plant.

June 1994 - The DPRK announces that it withdraws from the IAEA. Former US president Jimmy Carter negotiates a deal with the DPRK. The DPRK confirms it is willing to freeze its nuclear arms program and resume talks with the United States.

Oct. 1994 - The United States and the DPRK adopt the Agreed Framework in Geneva after four months of negotiations. Under the agreement, the DPRK is to freeze and eventually eliminate its nuclear facilities and to allow IAEA special inspections. In exchange, the DPRK will receive two light-water reactors (LWRs), along with annual shipments of heavy fuel oil.

March 1995 - The Korean Peninsula Energy Development Organization (KEDO) is set up with the United States, South Korea and Japan as the original members.

November 1999 - KEDO officials sign contract with the Korea Electric Power Corporation to begin construction of the two LWRs.

Jan. 2002 - US President George W. Bush describes the DPRK, Iran and Iraq as an "axis of evil."

Oct. 3-5, 2002 - US Assistant Secretary of State for East Asian and Pacific Affairs James Kelly visits the DPRK and reiterates US concerns about the DPRK's nuclear and missile programs and other disputes.

Oct. 16, 2002 - The United States announces that the DPRK admitted to having a covert programs to enrich uranium for nuclear weapons during Kelly's visit.

Oct. 25, 2002 - The DPRK Foreign Ministry says it will address US concerns about its nuclear program if the United States signs anon-aggression treaty, guarantees Pyongyang's sovereignty and pledges not to interfere in its economic development.

Nov. 14, 2002 - KEDO holds a meeting in New York and the United States decides to cut off fuel oil shipments to the DPRK.

Dec. 12, 2002 - The DPRK announces plans to immediately restart the Yongbyon reactor to generate electricity to make up for the cutoff of fuel oil shipments.

Dec. 27, 2002 - The DPRK tells the IAEA its inspectors are no longer needed at Yongbyon. UN nuclear inspectors leave the DPRK on Dec. 31.

Jan. 3, 2003 - The DPRK blames the United States for nuclear standoff but says it is willing to hold talks.

Jan. 6, 2003 - IAEA gives the DPRK one last chance to readmit inspectors or be reported to the UN Security Council for breaching nuclear safeguards.

Jan. 7, 2003 - The United States says it is willing to talk to the DPRK. IAEA says Pyongyang has "only a matter of weeks" to readmit inspectors.