By 1990, with the reform movement perestroika well under way in Russia and Eastern Europe, North Korea lost direct access to Soviet-supplied military and economic assistance.

In 1991, Pyongyang and South Korea set up a Joint Nuclear Control Committee to ensure neither side would stock nuclear weapons. Even so, South Korean officials remained concerned over the North's potential threat to its region: North Korea was suspected of having 134 arms factories, most covered or concealed underground.

In 1993, North Korea test-fired the Nodong I missile, a new ballistic missile that can travel more than 900 kilometers. Later that year, North Korea threatened to withdraw from the nuclear nonproliferation treaty. U.S. intelligence suggested Pyongyang was cooperating with Iran on developing nuclear weapons and ballistic missiles and the North barred international nuclear monitors from entering the country.

A U.S. News & World Report from March 1993 cited anonymous Western intelligence sources saying Iran and North Korea had struck a deal. The sources claimed Iran fronted up to $500 million for ballistic missiles development in exchange for North Korea's sale of nuclear weapons and designs for a plutonium reprocessing facility to Tehran.

The next year, North Korea and the United States reached a bilateral agreement, known as the Agreed Framework, that was intended to resolve the escalating concern over North Korea's nuclear capabilities. Under the Agreed Framework, the United States promised to supply the impoverished nation with two light-water reactors and other interim alternative energy resources, such as oil, as long as North Korea abandoned its nuclear program and shut down its Yongbyon reactor.

The 1994 agreement also stipulated that Pyongyang readmit International Atomic Energy Agency inspectors and renew its membership in the nonproliferation treaty. The agreement did not achieve the United States' desired goal of halting North Korea's arms industry.

In August 1998, North Korea launched the Taepodong I missile (ranging up to 2,000 km) over Japan and into the Pacific Ocean.

Several nongovernmental defense monitors reported that North Korea was developing or already possessed Taepodong-derived antiballistic missiles capable of reaching Alaska or Hawaii, and another missile capable of traveling to the continental United States.

Read about developments since 1998 in the North Korea Archive.

-- Compiled by Liz Harper for the Online NewsHour