North Korea didn't start trying to process the spent fuel rods until after Bush sabotaged the deal and stopped the heavy oil shipments that were part of the framework agreement. North Korea didn't know what the hell the US was doing. In 2002 the Bush administration accused N. Korea of having nukes and they denied it. Then in 2003 when North Korea started processing their spent fuel rods and said they had nukes, the US said they were bluffing....
"....CIA estimates in the 1990s about North Korean weaponry, however questionable and flawed, seem both careful and modest compared to the exaggerations of the Bush Administration and its emissary to Pyongyang, James Kelly. Coming into office when the CIA's 'one or two devices' estimate was nearly a decade old, Bush contrived to hype the threat, while at the same time downplaying the idea that its size made a difference: the North might have two or six or eight atomic bombs, but that didn't constitute a crisis. Rather, Saddam Hussein -- whom we now know to have been disarmed by years of UN inspections -- was so much more dangerous as to justify a preventive war. The result was chaos as far as US policy was concerned, and free rein for North Korean hardliners to move ahead with producing nuclear weapons.
Bush resisted holding high-level talks with Pyongyang for more than a year after assuming office, although the Clinton Administration had left on the table a tentative agreement to buy out all of the North's medium and long-range missiles. When Bush finally dispatched Kelly to Pyongyang in October 2002, Kelly accused the North of having a second nuclear programme, to enrich uranium and build more bombs by that method....
Within days of Kelly's return, Administration officials told the New York Times that the 1994 Agreement was dead. Then they cut off the supply of heavy heating oil that Washington had been providing as interim compensation under the Agreement. Pyongyang quickly announced that the Agreement had collapsed, withdrew from the Non-Proliferation Treaty, kicked out the UN inspectors, removed the seals and closed-circuit cameras from the Yongbyon complex, regained control of 8000 fuel rods that had been encased for eight years, and restarted their reactor. (Basically, this was a lock-step recapitulation of what they had done in 1993-94 in order to get Clinton's attention.) The North hinted darkly that the hostile policies of the Bush Administration left it no choice but to develop 'a powerful physical deterrent force'. In spite of all this, in the run-up to the invasion of Iraq, the Administration continued to downplay its own evidence that the North now had not one but two bomb programmes and refused to call the situation a 'crisis'. This clearly confused the North: 'When we stated we don't have a nuclear weapon, the USA [said] we do have it,' one DPRK general told a Russian visitor, 'and now when we are [saying] we created nuclear weapons, the USA [says] we're just bluffing.' ..."
Wrong Again:US policy on North Korea | The Asia-Pacific Journal
Chronology of U.S.-North Korean Nuclear and Missile Diplomacy | Arms Control Association