A timeline of nuclear weapons development in North Korea:
—1993: North Korea says it will quit the Nuclear Nonproliferation Treaty, later suspends its withdrawal.
—1994: North Korea, United States sign agreement in Geneva. The North pledges to freeze — and eventually dismantle — its plutonium-based nuclear weapons program in exchange for help building two power-producing nuclear reactors.
—Sept. 17, 1999: U.S. President Bill Clinton agrees to first major easing of economic sanctions against North Korea since the Korean War's end in 1953.
— Oct. 23-24, 2000: U.S. Secretary of State Madeleine Albright visits Pyongyang in trip by highest-ranking U.S. official ever to North Korea.
—Jan. 29, 2002: U.S. President George W. Bush labels North Korea, Iran and Iraq an "axis of evil."
—Oct. 4: North Korea tells visiting U.S. delegation it has a uranium enrichment program, Washington says.
—Nov. 11: U.S. and key Asian allies — Japan, South Korea — halt oil supplies to the North promised in 1994 deal.
—Jan. 10, 2003: North Korea says it will withdraw from the Nuclear Nonproliferation Treaty.
—Aug. 27-29: North Korea joins first round of six-nation nuclear talks, which include China, Japan, Russia, the U.S. and South Korea, and are held in Beijing.
—Feb. 25-28, 2004: Second round of six-nation talks.
—June 23-26, 2004: Third round of six-nation talks.
—Feb. 10, 2005: North Korea announces it has nuclear weapons.
—July 26: Fourth round of six-nation talks is held, ending in recess after 13 days with no agreement.
—Sept. 13: Six-nation talks resume.
—Sept. 15, 2005: U.S. blacklists Macau-based bank for alleged counterfeiting and money laundering by North Korea, leading the bank to freeze North Korean assets.
—Sept. 19: North Korea promises to dismantle nuclear programs in exchange for pledges of energy assistance; U.S. says it has no plans to invade, and will respect North's sovereignty in an agreement ending talks.
—Nov. 9-11: Fifth round of six-nation talks.
—Jan. 3, 2006: North Korea says it will not return to talks unless the U.S. lifts financial restrictions.
—July 5: North Korea launches seven missiles — including a long-range model — into the Sea of Japan, drawing international condemnation and a U.N. Security Council resolution condemning the act.
—Oct. 9: North Korea says it has conducted its first-ever nuclear test.
—Oct. 14: U.N. Security Council unanimously adopts a resolution imposing wide-ranging economic and diplomatic sanctions on North Korea for its nuclear test.
—Dec. 18-22: Six-nation talks meet in wake of nuclear test, no breakthrough made.
—Jan. 16-18, 2007: U.S. and North Korean envoys meet in Berlin.
—Feb. 13: North Korea agrees at six-nation talks on initial steps to disarmament, including shutting down its main nuclear facility within 60 days and eventually disabling its programs in exchange for aid equivalent to 1 million tons of heavy fuel oil.