Japanese Prime Minister Fumio Kishida on Wednesday told South Korean President Yoon Suk Yeol that a planned release of treated radioactive water from the wrecked Fukushima nuclear plant conforms to international standards and is safe.

During a meeting in Vilnius, held on the sidelines of a NATO summit, Kishida and Yoon also agreed to work toward holding high-level economic talks by the end of this year, the Japanese government said, as the neighbors have been moving quickly to improve ties long overshadowed by their wartime history.

Regarding the water discharge, Kishida promised Japan will take appropriate measures, including immediately suspending releases if the concentration of radioactive materials from the nuclear plant exceeds the level permitted under safety standards.

Opposition to the discharge remains strong in Japan's neighboring countries despite the International Atomic Energy Agency recently affirming that the move poses no risk to human health or the environment.

Yoon said South Korea "respects" the outcome of the U.N. agency's report that green-lit the Japanese plan, according to the government. But Yoon's office said he requested that Japan share real-time monitoring information and allow South Korean experts to participate in the safety checking process.

After nearly two years of an independent safety review, IAEA Director General Rafael Grossi submitted the report to Kishida last week in Tokyo. The discharge is expected to commence around this summer.

As Japan's relations with South Korea have dramatically improved under the Yoon administration after years of acrimony over historical issues, Kishida aims to ensure the plan does not derail the good momentum.

Japanese Prime Minister Fumio Kishida (R) and South Korean President Yoon Suk Yeol shake hands ahead of their talks in Vilnius, Lithuania, on July 12, 2023. (Kyodo)

The rapprochement of Japan and South Korea has been strongly welcomed by the United States, a vital security ally of both Asian nations, which is seeking to boost trilateral cooperation amid China's rising influence in the region.

While Japan and South Korea are not members of NATO, they were invited as important partners to the summit, where security affairs in the Indo-Pacific were also discussed.

The meeting in the Lithuanian capital took place just hours after North Korea test-fired its first intercontinental ballistic missile in three months, logging a record flight time for a projectile launched by Pyongyang.

Kishida condemned the latest launch during talks with Yoon, saying their bilateral and three-way cooperation with the United States needs to be strengthened.

The North Korean action "threatens the peace and security of the international community," Kishida said.

The missile, launched at a high angle from an area near Pyongyang, flew for about 74 minutes and 1,000 kilometers before splashing into the sea off Japan's northernmost main island of Hokkaido. It is estimated to have reached a maximum altitude of more than 6,000 km.

Kishida and Yoon, who last met in Hiroshima in May, expressed satisfaction with the improving relations between Japan and South Korea. The latest meeting marked their fourth already this year.

"As we usher in a new era of Japan-Korea relations together, I welcome the progress being made broadly, by both the government and the private sector," Kishida said.

Yoon said he believes the two countries working together will be of "great help in promoting peace and prosperity in the region and in resolving global issues."

He added that South Korea and Japan should work closely with NATO "to safeguard peace in the Indo-Pacific region."

Related coverage:

Fukushima fishermen still oppose water release after IAEA report

Japan strides for Fukushima water release as regulator OKs facilities

China urges ASEAN regional forum to oppose Fukushima water release