By Hyonhee Shin

SEOUL South Korean President Yoon Suk Yeol said on Tuesday that this week's summit with the leaders of the United States and Japan will set a new milestone in trilateral cooperation in the face of North Korea's evolving nuclear and missile threats.

In a speech marking the anniversary of his country's liberation from Japan's 1910-45 colonial rule, Yoon emphasised a need to step up security cooperation with Washington and Tokyo, through reconnaissance assets and real-time sharing of data on the North's nuclear weapons and missiles.

The summit "will set a new milestone in trilateral cooperation contributing to peace and prosperity on the Korean Peninsula and in the Indo Pacific region", Yoon said.

Yoon is set to join U.S. President Joe Biden and Japanese Prime Minister Fumio Kishida at the Camp David presidential retreat in Maryland on Friday, where they will launch a series of joint initiatives on technology, education and defence, senior U.S. officials said.

Since taking office in May 2022, Yoon has sought to improve relations with Tokyo, frayed by a stalemate in feuds over compensation suits raised by victims of Japan's forced labour during its colonial rule.

Japan says the issue was resolved under a 1965 treaty that normalised relations, but the strained ties have hindered U.S.-led efforts to bolster trilateral cooperation to curb North Korea's weapons programs.

Yoon has taken steps to compensate the victims with South Korean money, instead of Japanese funds, and visited Tokyo in March in the first such trip by a South Korean leader in 12 years.

"Korea and Japan are now partners who share universal values and pursue common interests," Yoon said in the speech, pledging to boost exchanges on security and economic issues.

The speech made no mention of security concerns related to other major powers in the region including China and Russia.

Washington has formal collective defence arrangements in place with both Tokyo and Seoul separately, but it wants those two countries to work closer together given growing concerns about China's mounting power and worries about its intentions.

Separately, South Korea's foreign ministry expressed regret after Kishida sent offerings to the Yasukuni shrine, seen as a symbol of wartime legacy as it honours World War II criminals.

Meanwhile, North Korea leader Kim Jong Un and Russian President Vladimir Putin exchanged letters on Tuesday pledging to develop ties into what Kim called a "long-standing strategic relationship", Pyongyang's state media KCNA said.

The United States has accused North Korea of providing weapons to Russia for its war in Ukraine, including artillery shells, shoulder-fired rockets and missiles. Pyongyang and Moscow have denied any arms transactions.

(Reporting by Hyonhee Shin; Editing by Ed Davies and Ed Osmond)