Defense Secretary Chuck Hagel said Tuesday that North Korea's nuclear weapons pose a "growing threat" to the United States and its allies, as Pyongyang raised tensions by blocking workers from a joint industrial zone.
Hagel phoned Chinese Defense Minister Chang Wanquan Tuesday evening and asked Beijing to help intensify pressure on the North Koreans to abandon their pursuit of additional nuclear weapons and ballistic missiles.
The call came shortly before North Korea moved to bar South Korean workers from a jointly operated factory park. The Kaesong zone, just over the North Korean border, is home to 100 factories and employs some 50,000 North Koreans, according to the BBC. Several hundred South Korean managers regularly travel across the border into the zone, which generates some $2 billion in economic activity for the impoverished North.
North Korea has barred workers from the South before — most recently in 2009, because of U.S. military exercises in the region. But the move is a sign that relations are deteriorating in the region.
"South Korea's government deeply regrets the entry ban and urges it be lifted immediately," Unification Ministry spokesman Kim Hyung-seok told the BBC.
North Korea's actions are thought to be driven by additional United Nations sanctions that resulted from its recent nuclear test. The North Korean regime has since disconnected its so-called "red phone" with the South, declared a "state of war" and threatened the United States with a nuclear attack.
The U.S. has responded with a series of military drills in the region, as well as a repositioning of naval ships in waters off the Korean peninsula.
On Tuesday, the White House said it was "taking appropriate measures in response to the bellicose rhetoric and provocative actions" from North Korea.