The move comes a day after the reclusive communist regime handed over long-awaited details of its nuclear program, but no account of its weapons stockpile.
In return, President Bush announced Thursday that the United States would remove Pyongyang from terrorism and sanctions blacklists, the latest concession aimed at prodding the communist regime to abandon its nuclear program.
Hours after the destruction of the cooling tower, North Korea's Foreign Ministry said in a statement that it "positively assesses" and "welcomes" the U.S. measures, and also urged Washington completely withdraw its "hostile policy" toward Pyongyang.
The tower destruction was not mentioned by the North's media or shown on state TV broadcasts.
"This is a very important step in the disablement process and I think it puts us in a good position to move into the next phase," said Sung Kim, director of the U.S. State Department's Korea office, who attended the demolition, according to the Associated Press.
The tower explosion came 20 months after Pyongyang detonated a nuclear bomb in an underground test to confirm its status as an atomic power. The nuclear blast spurred an about-face in the U.S. hard-line policy against Pyongyang, leading to the North Korea's first steps to scale back its nuclear weapons development since the reactor became operational in 1986.
Last year, the North switched off the reactor at Yongbyon, 60 miles north of the capital Pyongyang, and it already has begun disabling the facility under the watch of U.S. experts so that it cannot easily be restarted.
"This was an active reactor," U.S. Secretary of State Condoleezza Rice said in Kyoto, Japan, where she is attending meetings of the Group of Eight industrialized countries.
"This was a reactor that was making plutonium, that made enough plutonium for several devices including one that was tested in 2006 so it was important to put North Korea out of the plutonium business."
North Korea's nuclear declaration, which was delivered six months later than the country promised and has not yet been released publicly, is said to only give the overall figure for how much plutonium was produced at Yongbyon, but no details of bombs that may have been made.
Experts believe the North has produced enough weapons-grade plutonium for as many as 10 nuclear bombs.
"[W]e have to hope ... the documents they provided will, in fact, be verifiable, the information they've provided will mean something, and that the cooling tower won't be rebuilt after it's exploded," Chuck Downs, executive director of the U.S. Committee for Human Rights in North Korea, said Thursday on the NewsHour. "The 19,000 pages of documents have yet to be proven to be actual documents. These things are very much up in the air."