A nuclear North Korea. (International).

Credit James A. Kelly, U.S. Assistant Secretary of State, with expert sleuthing. In early October, Kelly discovered that Communist North Korea was secretly developing nuclear weapons.

At first, North Korean officials angrily denied Kelly's claim. A day later, they fessed up.

"They told us they had a program," says one U.S. official, "then [they] told us our current agreements meant nothing anymore."

In 1994, the U.S. and North Korea signed a treaty known as the "Agreed Framework." Negotiated under President Bill Clinton, the accord required North Korea to stop using a nuclear reactor which produced plutonium strong enough for nuclear weapons. The U.S., in turn, agreed to help finance new "light water" reactors, which generate electric power but not nuclear material.

The revelation that North Korean President Kim Jong II has been defying the treaty stunned the world, especially neighboring countries like Japan and South Korea. Those nations would be most vulnerable to an attack.

President George W. Bush greeted the news with anger. But he soon said that the U.S. would use diplomatic efforts to persuade North Korea to stop building nuclear arms.

That decision complicated President Bush's arguments for using force against Iraq. Why attack one dangerous nation and negotiate with the other?

"We do believe that we have [diplomatic] ways to deal with North Korea," says National Security Adviser Condoleezza Rice. "[But] we have tried just about everything with Iraqi President Saddam Hussein ... and nothing has worked."