SEOUL, South Korea — North Korea threatened retaliation against South Korea for demanding talks aimed at re-opening a jointly run industrial park that has been shuttered for more than two weeks.

The North will take “final, decisive and serious measures” if President Park Geun Hye’s government continues to issue ultimatums, the National Defense Commission said in a statement on the official Korean Central News Agency.

Kim Jong Un’s regime Friday day ignored a noon deadline to accept an offer for talks on the Kaesong industrial zone or face what the South’s Unification Ministry said would be “serious measures.”

The Korean peninsula has been on edge since February, when Kim Jong Un’s regime detonated an atomic bomb in defiance of United Nations sanctions then threatened preemptive nuclear strikes against its enemies.

The North on April 8 recalled its workers from Kaesong, the last point of inter-Korean exchange and an important cash source for its impoverished nation.

The complex, about 10 kilometers (6 miles) north of the demilitarized zone between the two countries, employs more than 53,000 North Koreans at 123 South Korean companies. North Korea generates $100 million in annual profits there, while South Korea makes quadruple that amount, according to Yang Moo Jin, a professor at the University of North Korean Studies in Seoul.

The South should withdraw all remaining citizens if concerned about their well-being, KCNA said, adding that relevant North Korean organizations will “responsibly provide all assistance” to guarantee their safety.

Entry Ban

Park said at meeting of national security officials that it is unclear whether South Korea “must wait indefinitely” for the Kaesong situation to normalize, according to a statement on her website.

North Korea on April 3 blocked South Korean access to the complex only allowing them to leave. Currently 176 South Korean executives and managers voluntarily remain in Kaesong, and none plan to return to Seoul today, Unification Ministry spokesman Kim Hyung Suk said.

Since all traffic from the South into Kaesong was banned, remaining South Koreans have been suffering from a shortage of food and medical resources. One citizen returned to Seoul yesterday after suddenly falling ill, the Unification Ministry said.

With the United States and South Korea calling on North Korea to return to negotiations, Park’s options in pressuring Kim over Kaesong “are very limited,” said Kim Young Yoon, a research fellow at the Korea Institute for National Unification in Seoul.

Jeopardizing Efforts

“Removing South Korean workers, assets and companies from Kaesong or taking some military action against the North for not responding to calls for dialogue will jeopardize all diplomatic efforts and what little that’s left to salvage deteriorated ties,” said Kim.

South Korean companies operating there have urged the government to break the impasse and address damages from the loss of operations. The association representing them yesterday issued a statement calling for talks between the two countries “as soon as possible.”

The warning from Park’s government is probably “in response to domestic public opinion, which is souring over the concerns for the losses being incurred,” analyst Kim said.

Kim Jong Un, who took over as leader in December 2011 following the death of father Kim Jong Il, has rebuffed international inducements to abandon nuclear weapons development.

The Obama administration has rejected claims North Korea possesses the ability to launch nuclear-armed ballistic missiles while warning Kim’s inexperience raises the possibility of errors.

Miscalculation Risk

The risk of a miscalculation in the dispute over North Korea’s nuclear and missile programs has increased, the chairman of the U.S. Joint Chiefs of Staff said April 24 in Beijing. China, North Korea’s biggest ally, regards the situation “very seriously,” General Martin Dempsey told reporters after meeting officials including President Xi Jinping.

China regards its neighbor as a strategic buffer with U.S.- backed South Korea. Secretary of State John Kerry said ahead of meetings this month in Beijing that Xi’s government needs to “put some teeth” into restraining Kim’s regime.

In a sign of greater cooperation, China’s North Korea envoy, Wu Dawei, visited Washington and discussed North Korea with Undersecretary of State Wendy Sherman, Foreign Ministry spokeswoman Hua Chunying said Thursday. Deputy Secretary of State William Burns is visiting Beijing and Seoul this week.

The North is ready to conduct another nuclear test “at any moment,” South Korean Defense Ministry spokesman Kim Min Seok said April 23. North Korea vowed to strengthen its nuclear program after a State Department report found the country guilty of “egregious and pervasive” human-rights abuses.

South Korean Foreign Minister Yun Byung Se met Chinese counterpart Wang Yi April 24 in Beijing. The talks paving the way for the start of a three-way “strategic dialogue” with the United States over issues including North Korea, Foreign Ministry spokesman Cho Tai Young told reporters Thursday in Seoul.