Christopher Hill, former chief U.S. nuclear negotiator with North Korea, says it was his idea to blow up the cooling tower at North Korea's main Yongbyon nuclear complex as a symbol of progress in nuclear negotiations.

Hill, who served as chief U.S. delegate to the six-party nuclear talks from 2005 to 2009, recalled the 2008 incident in his memoir, titled "Outpost: Life on the Frontlines of American Diplomacy," saying he first brought up the idea of destroying the tower with his North Korean counterpart, Kim Kye-gwan.

"I had first raised the idea of blowing up the tower with Kim Gye-gwan, pointing out that the event would be watched around the world and would help us overcome any doubts that our journey – at least on the plutonium production -- was real," he said in the book.

Kim was interested, but cautious, Hill said.

Hill said he also told his Chinese counterpart, Wu Dawei, that there should be "a gesture that would give meaning to all the sawing of exhaust pipes and other disabling steps."

"As I spoke I was rolling my notes into the shape of a cylinder and stood them on end. When Wu asked what I had in mind, I told him, 'We should collapse the cooling tower like this,' slamming the

spindled notes with the palm of my hand. Eyeing my crushed notes on the table, he said, 'We'll convince them,'" Hill said.

The North's destruction of the cooling tower briefly raised hopes for real progress in the six-party talks aimed at ending the North's nuclear program, but the negotiating process later reached

a deadlock over how to verify the North's declaration of nuclear materials, facilities and activities.

In exchange for blowing up the tower, the North was removed from the U.S. list of states sponsoring terrorism. Six-party talks were convened one more time later in 2008, but the negotiations have since been stalled. That has reinforced criticism that Pyongyang abuses the negotiations only to win concessions.

Since then, the North has conducted two more nuclear tests, in 2009 and 2013, as well as a series of long-range rocket launches in an effort to develop intercontinental ballistic missiles capable of reaching the U.S. mainland with nuclear warheads.

North Korea has called for resuming the six-party talks without any conditions, but the U.S. and South Korea demand that Pyongyang first take concrete steps demonstrating it is serious about its commitment to give up its nuclear program. (Yonhap)