Photo/IllutrationThere are signs of landslides in the lower left of this aerial photo of the Punggyeri nuclear test site. (Provided by 38 North)

SEOUL--North Korea has moved to halve troop strength at its Punggyeri nuclear test site, possibly signaling its hopes of an imminent rapprochement with the United States, according to well-placed sources.

The decision to downsize troop numbers may be in anticipation that an expected meeting in May between U.S. President Donald Trump and North Korean leader Kim Jong Un will lead to a deal that results in North Korea's denuclearization in exchange for full bilateral relations, economic assistance and security guarantees.

However, the sources said it would not be difficult to resume operations at Punggyeri if the talks fail to produce substantial results. On the other hand, this latest move by North Korea could be a step toward the eventual closing of the facility.

Sources said the order was issued early this month to the 19th regiment that is deployed in and around the test site. Transfer orders were issued to two of the four battalions that have been in charge of digging tunnels at the site for underground nuclear tests.

The four battalions have a total strength of about 1,000.

Two battalions remain at the test site, along with about 150 members of an engineering corps battalion and 70 or so members of a military company in charge of security.

If an agreement is reached at the Trump-Kim summit to denuclearize North Korea, the remaining troops at Punggyeri could also be moved and the site closed.

Such a move would follow in the footsteps of past agreements. In June 2008, North Korea destroyed a cooling tower for a nuclear reactor at a nuclear-related facility at Yongbyon as a way to demonstrate Pyongyang was adhering to an international agreement on denuclearization.

But sources said North Korea would only go ahead with the concessions based on steps Washington would take in response to demands from Pyongyang.

During meetings at the highest leadership levels within North Korea, it was explained that nuclear tests are no longer a necessity as the completion of such weapons is now a fait accompli, the sources said.

It was also explained that even if a denuclearization agreement was reached, it would take at least a decade to destroy the nation's nuclear arsenal.

During a meeting with special envoys from South Korea on March 5, Kim Jong Un said that there would be no need to possess nuclear weapons if the security of the North Korean regime was ensured and military threats against it erased.

North Korea is expected to ask the United States to sign a peace agreement in exchange for denuclearization. Among other proposals under consideration in Pyongyang is a ban on the approach of strategic bombers carrying nuclear weapons to the Korean Peninsula.

"Shutting down the Punggyeri site is not a major issue," said a source with a strong grasp of North Korean affairs. "If North Korea-U.S. relations deteriorate, all that would have to be done is resume nuclear tests."

There are other signs that the Punggyeri site may no longer be usable.

Construction at the site is believed to have begun in the late 1980s after troops were stationed in the area. Six nuclear tests were conducted there between October 2006 and September 2017.

But the last test led to a landslide on nearby Mount Mantap, apparently because it was weakened by the nuclear blasts.

South Korean experts pointed out that further tests at Punggyeri would be impossible because of the danger that radiation would leak if the program was resumed.