Japan and the United States are moving to lead international debate over sanctions against North Korea in the wake of the country's announcement that it has successfully carried out a hydrogen bomb test.

Prime Minister Shinzo Abe had a 20-minute telephone conversation with U.S. President Barack Obama on the morning of Jan. 7 in response to the North's nuclear experiment. The two leaders confirmed that they would cooperate with South Korea and other countries concerned and lead discussions on new sanctions against North Korea at the United Nations Security Council.

During the talks, Abe denounced North Korea, saying, "It poses a serious threat to peace and security in the region and the international community." The prime minister added, "It is important for the global community to take a firm response in order to prevent further provocative actions. We will take a swift response to the matter through close cooperation between Japan, the United States and South Korea as well as with other countries concerned."

In response, President Obama said his country would take every possible measure to protect the security of Japan and other allies. He also agreed to start talks on new sanctions against North Korea at the earliest date possible by seeking cooperation in discussions at the U.N. Security Council.

With regards to Japan and South Korea's "final and irreversible" agreement over the wartime "comfort women" issue reached on Dec. 28 last year, Prime Minister Abe thanked the U.S. for its understanding and cooperation. President Obama hailed the improvement of ties between Tokyo and Seoul, saying that the bilateral accord would help collaboration between Japan, the U.S. and South Korea to greatly contribute to peace and stability and to work even more effectively at the United Nations.

President Obama also had a telephone conversation with South Korean President Park Geun-hye on Jan. 6 (Jan. 7 Japan time), in which they agreed on international cooperation toward an integrated response to the North's nuclear experiment, according to the White House.

During a House of Councillors plenary session on Jan. 7, Prime Minister Abe highlighted the outcome of his telephone talks with President Obama, saying, "We have agreed that Japan and the U.S. would lead the international community including a response by the U.N. Security Council. I have also reaffirmed a solid U.S. commitment to defend Japan by every means possible." He added, "We will strive to achieve an integrated response by the international community and will take a firm and stern response including considering our country's own measures."

Japan currently imposes two types of sanctions -- one based on a U.N. Security Council resolution and the other unique to Japan. In July 2014, Japan lifted part of its own sanctions against the North in response to the latter's launch of a special investigation committee to reinvestigate the abduction of Japanese nationals by North Korean agents.

The lifted sanctions include barring North Korean nationals and North Korean government employees from entering Japan and calling on Japanese to refrain voluntarily from traveling to North Korea, obliging Japanese to report on any taking of more than 100,000 yen in cash to the North and on money transfers of more than 3 million yen to the country, and barring port calls by a North Korean-registered vessel for humanitarian purposes. A government source said there is a possibility that those sanctions would be reinstated.

Regarding the North's announcement that it has successfully conducted a hydrogen bomb test, Deputy Chief Cabinet Secretary Koichi Hagiuda told a Jan. 7 press conference, "We are striving to verify the facts. At the moment, we haven't determined it was an H-bomb test." He also disclosed that there were no changes in radiation levels in Japan.

Foreign Minister Fumio Kishida also held telephone talks with U.S. Secretary of State John Kerry on the morning of Jan. 7. Kishida pointed out that the North's nuclear test was "an act of defiance to the nuclear non-proliferation system." In response, Kerry stated that the North needed to pay the cost for its actions, suggesting the need to step up sanctions against North Korea.