South Korea’s foreign minister warned North Korea on Tuesday that the cost of keeping and testing nuclear weapons will be so high that it could threaten the survival of Kim Jong Un’s regime.

Yun Byung-se told a standing-room audience of diplomats, U.N. officials and Korea-watchers at the International Peace Institute that the North will pay “the heaviest price” in new sanctions if it defies the international community and goes ahead with a new nuclear test.

Many experts — and the South Korean government — had suspected the North would conduct its fourth nuclear test during President Barack Obama’s recent visit to Seoul. North Korea has said it still may go ahead and test a new kind of nuclear device following Obama’s visit.

“Our assessment is that North Korea is ready to undertake a test whenever they make the necessary political decision,” Yun said.

A call to North Korea’s U.N. Mission seeking comment was not answered.

He explained that a new test “will make a great impact on the strategic landscape in our part of the world” and could undermine the Nuclear Nonproliferation Treaty, the cornerstone of global nuclear disarmament efforts. North Korea has pulled out of the treaty.

Faced with this challenge, Yun said South Korea has been making intensive diplomatic efforts to deter the North from carrying out a new test with the other parties to the stalled six-party nuclear talks aimed at reining in the North’s nuclear program, Security Council members, the European Union and Asian nations.

In the event of a new test, he said, the U.N. Security Council must fill all loopholes in the four rounds of sanctions it has already imposed on the North over its nuclear and ballistic missile programs — and individual countries must take similar tough measures.

As long as North Korea relies on nuclear weapons to make threats, Yun warned, “then we, South Korea, together with our partners in the Security Council, will make the cost of having these nuclear weapons very very high, very very heavy, so that could backfire to the regime — the survival of the regime.”

At the same time, Yun stressed that South Korean is seeking to build a peaceful and “new Korean peninsula.”

He reiterated President Park Geun-hye’s proposals last month to reunify Korea, which has been divided along the world’s most heavily fortified border since the 1950-53 Korean War ended with an armistice, not a peace treaty.

“It takes two to tango,” he said. “We hope North Korea will respond positively to our genuine proposals.”

Yun said South Korea “recognizes that our journey for reunification will be long and bumpy” but he said a nuclear-free and unified Korea would alleviate security threats in northeast Asia and stabilize the region.

“The geopolitical plate of the region is going through what I would call tectonic shifts,” he said. “We are witnessing a rising China, a resurgent Japan, an assertive Russia and an anachronistic North Korea which is simultaneously pursuing nuclear weapons and economic development.”

Yun said conflicts over history, territory and maritime security, among others, are raising concerns “that even a military confrontation owing to miscalculations may become a reality.”

At the heart of these conflicts, he said, is “a trust deficit.”

Yun said that’s why South Korea is seeking to unify the two Koreas and build a new Asia and a new world.

Yun said he is “rather optimistic about this unification” because there are changes inside North Korea and many changes outside including China and Russia now saying publicly for the first time that they are in favor of peaceful reunification of the Koreas.

“We have to be prepared for that possibility, or any scenario that will be unfolding in the coming months and years,” he said

He recalled the day 23 years ago when East Germany and West Germany replaced their two nameplates at the United Nations with a single nameplate that said Germany.

“Likewise, I do believe the day is approaching, perhaps much faster than we may all realize, for the two Koreas to replace their respective nameplates with one single nameplate that simply says Korea,” Yun said.

(AP)