Flexing its nuclear muscles again, North Korea has moved further away from the Sept. 19 Joint Statement once hailed as a historic deal on ending its nuclear program.

The 10th anniversary this week of signing the agreement is far from a celebratory mood.

Another round of the nuclear crisis is instead descending on the region, where the national interests of South Korea, the United States, China, Japan and Russia go head-to-head, while, at the same time, the countries work together for peace and stability, experts said.

The North announced Tuesday that it has put all its nuclear bomb fuel production lines back in operation. It said it is ready to use nuclear weapons "at any time' against the U.S. and other "hostile" nations.

Pyongyang also strongly indicated a plan to launch another long-range rocket around the Oct. 10 founding anniversary of its communist party.

The North's fourth nuclear test may follow, given the pattern of its strategic provocations.

"We can say that (the world) has entered the third North Korean nuclear crisis," said Chang Yong-seok, senior researcher at the Seoul National University Institute for Peace and Unification Studies.

He cited the North's self-declaration in its constitution as a nuclear power and leader Kim Jong-un's stated policy of developing its nuclear program and economy simultaneously.

"The task of resolving the North Korean nuclear issue has become even more difficult," compared with the first crisis in the early 1990s and the second one in the 2000s, Chang pointed out.

The North has continued to upgrade its nuclear capability amid a drawn-out stalemate in the six-party talks.

South Korea's defense ministry formally estimates that the secretive North has more than 40 kilograms of weapons-grade plutonium, enough to produce at least seven nuclear bombs. Concerns are growing about the level of the North's technology in miniaturizing nuclear weapons to mount on missiles.

The Sept. 19 document issued at the conclusion of the fourth round of six-party talks in Beijing initially raised hopes of significant progress in denuclearizing the North and bringing lasting peace to the peninsula.

In the deal, Pyongyang "committed to abandoning all nuclear weapons and existing nuclear programs and returning, at an early date, to the Treaty on the Nonproliferation of Nuclear Weapons and to IAEA safeguards."

The regional powers agreed to provide the North with massive energy aid in return. Washington and Japan promised to take steps to normalize ties with Pyongyang.

The North submitted a declaration of its nuclear stockpile and blew up a cooling tower at its Yongbyon nuclear complex in a symbolic gesture.

But the North and the U.S. walked out of the nuclear talks in December 2008, failing to reach a compromise on verification.

The Sept. 19 Joint Statement is now treated as a mere scrap of paper.

"The biggest problem is that North Korea has no will for denuclearization," said Chun Yung-woo, a former South Korean national security adviser. "The North will never abandon its nuclear weapons before (its dialogue partners) make the case that there will be more gains from giving them up than keeping them."

He stressed the need for the U.S. to be more active in dealing with the North Korea issue as it has done in the Iranian nuclear crisis.

A silver lining is that Beijing appears to be getting tough on Pyongyang. President Park Geun-hye of South Korea and her Chinese counterpart, Xi Jinping, agreed in their summit in early September to push for the resumption of the "meaningful" six-party talks.

It remains uncertain, however, whether the North will return to dialogue with the Barack Obama administration with just about 16 months left in power.

"As a U.S. policy priority, the denuclearization of North Korea is a policy corpse -- it is dead," said Larry Niksch, a U.S. expert who has long followed North Korea affairs.

Kim Sung-han, professor at Korea University in Seoul, called for the freezing of the North's nuclear activity first.

"And then, the two Koreas, the U.S. and China need to hold four-way peace talks to replace the Armistice Agreement with a peace treaty," he said. (Yonhap)