With North Korea seen as plunging deeper into isolation, concerns are growing over the absence of communication channels with Pyongyang and possible military provocation stemming from miscalculations.

Pyongyang’s state media said Monday it will “completely” shut down its telephone line with the U.S. in New York in protest against Washington’s recent sanctions on North Korean leader Kim Jong-un over human rights abuses.

The so-called New York channel, based in the communist state’s permanent mission to the U.N., had for years served as a main communication link between the two countries.

While the severance bears meanings more symbolic than literal, some Seoul officials and observers raised concerns over the escalating tension surrounding the peninsula which may lead to an unanticipated military provocation in South Korea.

“As virtually all exchange channels were closed and sanctions continue to tighten over not only nuclear and missile programs but also human rights and other aspects, the North could feel much more challenged in terms of its security and leadership stability and stage a provocation in a bid to shift the current situation,” a diplomatic source said, requesting anonymity due to the sensitivity of the issue.

Last Wednesday, the U.S. State Department and Treasury placed Kim on its sanctions blacklist for the first time, stepping up pressure on the regime over political prison camp operations, arbitrary executions, slave labor, torture and other brutalities against the North Korean people. The North condemned the move as an “an open declaration of war.”

Seoul and Washington then announced Friday that they will deploy a Terminal High Altitude Area Defense battery, advanced U.S. missile defense assets, by the end of next year to better counter evolving North Korean threats.

Pyongyang soon threatened to “physically act” against the stationing, and make the allies “suffer from the nightmare of extreme uneasiness and terror.”

These add to the already frosty cross-border situation since the North carried out its newest atomic and long-range rocket tests in January and February, respectively, which prompted Seoul to declare a halt of nearly all economic and humanitarian cooperation until Pyongyang changes its behavior. 

Yet the Kim regime shows no signs of shifting its course, and no exit strategy appears to be in store. Prime Minister Hwang Kyo-ahn on Tuesday reiterated that now is the time to urge a change, and after that, the government would explore what it would do.

“Given North Korea’s continuous development of nuclear weapons, it’s important to craft a response to a nuclear provocation at this stage,” he told the National Assembly.

Possible provocation scenarios, ahead of next year’s presidential election in particular, include an armed clash near the western sea border, other forms of a limited attack entailing casualties similar to last year’s landmine planting, or a large-scale cyberattack. Another underground nuclear test or Musudan intermediate-range ballistic missile firing could be conceivable, officials said.

In Washington, the U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies said Tuesday that recent commercial satellite imagery indicated a “high-level activity” at the North’s nuclear test site in the northwest town of Punggye, citing the presence of equipment, vehicles and several mine ore carts.

“Based on imagery alone, it is not possible to determine whether this activity is for maintenance, excavation or preparation for a fifth nuclear test,” the think tank said on its 38 North blog.

“Nevertheless, it is clear that North Korea is ensuring that the facility is in a state of readiness that would allow the conduct of future nuclear tests should the order come from Pyongyang.”

Seoul’s Unification Ministry said Pyongyang is “all ready to commit another nuclear test upon the order of Kim.” “We’re fully prepared, utilizing the South Korea-U.S. joint assets,” a senior official told reporters on customary condition of anonymity.

The U.S. State Department brushed off the North’s declaration of the closure of the New York channel, urging it to refrain from actions and rhetoric that “only further raise tensions in the region.”

“None of the rhetoric we’ve seen of late is doing anything to increase security and stability on the peninsula,” spokesman John Kirby said at a regular news briefing.

The U.S. Department of Defense spokesperson Cmdr. Gary Ross also defended the THAAD decision, saying it is the outcome of the North’s continued belligerence and ongoing pursuit of nuclear and ballistic missile capabilities.

“Incidents like this only confirm the prudence of our alliance decision, and we will continue to ensure that our defense posture remains capable of deterring conflict and defending ourselves and our allies,” he was quoted as saying by Yonhap News.

By Shin Hyon-hee (heeshin@heraldcorp.com)