North Korea announced on Dec. 4 that it conducted a successful hydrogen bomb nuclear test of a miniaturized warhead. Nuclear experts remain uncertain of the type of nuclear weapon tested and its explosive yield but agree that North Korea did conduct its fourth nuclear test.

North Korean leader Kim Jong-un asserted last month that his country had built a hydrogen nuclear bomb to “defend its sovereignty and the dignity of the nation.” Kim’s assertion about hydrogen bombs was met with expert skepticism, and it may be more likely that Pyongyang has achieved a boosted fission rather than a fusion bomb. Such a weapon would be larger than its first three nuclear tests (and the 1945 U.S. atomic weapons) but not of the magnitude from a hydrogen fusion bomb.

North Korea’s fourth nuclear test, particularly of an improved weapon, is a dangerous development. Coupled with ongoing development of several different missile systems, North Korea poses an increasing direct threat to the United States, South Korea and Japan. Experts estimate that Pyongyang currently has 10-16 nuclear weapons with potentially as many as 50-100 by 2020. North Korea has likely already achieved warhead miniaturization, the ability to place nuclear weapons on its medium-range missiles targeting South Korea and Japan, and a preliminary ability to reach the continental United States with a missile.

What Washington should do:

Washington should be consulting with Seoul and Tokyo to devise a common response to a North Korean missile launch. The allied response should include:

Convene the UN Security Council to implement a new resolution to impose strong punitive sanctions and close loopholes, such as including Article 42 of Chapter VII of the UN Charter, which allows for enforcement by military means. This would authorize naval ships to intercept, board and inspect North Korean ships suspected of transporting precluded nuclear, missile and conventional arms, components or technology.

Call upon all UN member nations to fully implement existing UN resolution requirements to prevent North Korea’s procurement and export of missile-related and WMD-related items and technology and freeze the financial assets of any involved North Korean or foreign person, company or government entity.

Publicly identify and sanction all foreign companies, financial institutions and governments assisting North Korea’s nuclear and missile programs. Target financial and regulatory measures against any entity suspected of helping North Korean nuclear, missile and conventional arms; criminal activities; money laundering; or import of luxury goods.

Impose third-party sanctions. The United States should penalize entities, particularly Chinese financial institutions and businesses, that trade with those on the sanctions list or export prohibited items. The United States should also ban financial institutions that conduct business with North Korean violators from access to the U.S. financial network.

Augment U.S. sanctions. President Obama’s assertion that North Korea is the most heavily sanctioned country in the world is simply not true. Washington has targeted fewer North Korean entities than those of the Balkans, Burma, Cuba, Iran and Zimbabwe. The United States has targeted more than twice as many Zimbabwean entities than North Korean.

For its part, South Korea should:

Maintain the resumed propaganda broadcasts along the DMZ as well increasing broadcasting into North Korea including using drones along the North’s coasts, and removing any restrictions on non-government organizations sending information leaflets via balloons into North Korea.

Sever its involvement in the Kaesong industrial park. Since its inception, the Kaesong venture failed to achieve its primary objective of inducing economic and political reform in North Korea and moderating the regime’s belligerent foreign policy.

Request U.S. deployment of the Thaad missile defense system. South Korea’s indigenous missile defense system is insufficient to defend against North Korea’s growing nuclear and missile threat.

Conclusion:

North Korea’s nuclear test reflects Pyongyang’s continued pursuit of its prohibited nuclear weapons programs despite countless attempts by the United States and its allies to reach a diplomatic resolution. It is time for the Obama administration to abandon its policy of timid incrementalism and fully implement existing U.S. laws by imposing stronger sanctions on North Korea and work with Congress to determine additional measures. Seoul should also take steps to better defend its citizens from North Korean threats.