1962: Sets up nuclear research center with Soviet help.
1979: Starts building first of three reactors capable of producing plutonium.
1985: Signs Non-Proliferation Treaty (NPT).
1989: Extracts enough plutonium for one or two bombs, according to the Central Intelligence Agency. Proposes talks with the South on denuclearizing both nations.
1991: Threatens to withdraw from NPT, forcing US to remove nuclear weapons from South Korea. Signs peace pact with South promising inspections.
1992: After a seven-year delay, allows first inspection by International Atomic Energy Agency. US and IAEA then find that the North lied about plutonium extraction.
1993: Bars inspectors from two key nuclear sites; announces withdrawal from NPT. President Clinton warns North Koreans that using nuclear weapons ``will be the end of their country as they know it.'' North tests a 600-mile-range missile in Sea of Japan; tries to hire Russian nuclear scientiests unsuccessfully; agrees with US to allow inspections.
1994: Allows limited access to inspectors, who find seals broken in plutonium-producing area. US breaks off talks. UN Security Council issues statements calling on North to resume inspections by mid-May with implied threat of possible economic sanctions.
Source: Wisconsin Project on Nuclear Arms Control.