U.S. Secretary of State Antony Blinken and Secretary of Defense Lloyd Austin are headed to South Korea after a frank set of talks on North Korea and China with Japanese allies.

U.S., Japan Talk of China's Challenge

In Tokyo, Blinken reassured Japan that the U.S. will continue to defend its Asian ally "through the full range of its capabilities, including nuclear."

Japan and China are still in dispute over the Senkaku Islands. Japan is currently in control of the disputed location at the East China Sea.

Japanese defense minister Nobuo Kishi and Austin also raised concerns over a new Chinese law that authorizes its coast guard to open fire on intruders, should they step into what China believes is within its territorial waters.

A joint statement released Tuesday after the meetings between Japanese ministers and American secretaries of state and defense stated that China's latest moves present "political, economic, military and technological challenges to the Alliance and to the international community."

The arrival of Blinken and Austin in Asia to improve the new administration's diplomatic ties in the region came at a time when the world has yet to see Chinese president Xi Jinping and U.S. president Joe Biden come face-to-face.

China has not yet issued comments regarding the recently-concluded U.S.-Japan alliance talks. A spokesman for the Chinese foreign ministry said that the alliance will help promote stability in the region.

Pyongyang Warns U.S. Ahead of South Korea Meetings

After the Tokyo meetings, Blinken and Austin are expected to be in South Korea next, as the U.S. seeks to strengthen ties with the country.

However, a stark warning from Kim Yo Jong, the sister of North Korea's leader, Kim Jong Un, said that the United States should "refrain from causing a stink" while visiting some Asian countries.

Kim, who has become more powerful in the North Korean government over the past few years, criticized the joint military exercises in the region between American and South Korean troops.

Being more specific, Kim said the U.S. should be more careful in its "first step" if it "wants to sleep in peace for the coming four years," a reference believed by analysts to be a direct hit at the Biden administration.

A similar warning was issued by Pyongyang during the early days of former U.S. president Donald Trump's presidency.

During a Tuesday news briefing in Japan, Blinken confirmed that the Biden administration tried to reach out to North Korea in mid-February but has not yet received a response from the North Korean government.

Blinken said it has been more than a year since "active dialogue" with Pyongyang took place. He added that the U.S. made "multiple attempts" to resume talks but to no avail.