The North Koreans have been pursuing nuclear weapons in violation of agreements long before Bush was elected.

From this source:

North Korea’s secret uranium enrichment program appears to date from at least 1996. Hwang Jang-yop, a Communist Party secretary who defected in 1997, has testified that North Korea and Pakistan agreed in the summer of 1996 to trade North Korean long-range missile technology for Pakistani uranium enrichment technology.

The Clinton Administration reportedly learned of it in 1998 or 1999, and a Department of Energy report of 1999 cited evidence of the program. In March 2000, President Clinton notified Congress that he was waiving certification that “North Korea is not seeking to develop or acquire the capability to enrich uranium.”

The Japanese newspaper, Sankei Shimbun, reported on June 9, 2000, the contents of a “detailed report” from Chinese government sources on a secret North Korean uranium enrichment facility inside North Korea’s Mount Chonma. Reportedly, according to a CIA report to Congress, North Korea attempted in late 2001 to acquire “centrifuge-related materials in large quantities to support a uranium enrichment program.” The CIA estimated publicly in December 2002 that North Korea could produce two atomic bombs annually through uranium enrichment beginning in 2005. Administration officials have stated that they do not know the locations of North Korea’s uranium enrichment program.

If nothing else, even if you discard all the evidence of a secret nuclear program prior to the Bush Administration, it is a firm fact that North Korea has been developing ICBMs all through the 1990s, with target payloads of about 200 kg to the U.S. mainland.

You tell me what weighs 500 lbs. that's worth putting on an ICBM to the American mainland.