PALO ALTO, California - South Korean President Yoon Suk Yeol and Japanese Prime Minister Fumio Kishida pledged cooperation on clean-energy supply chains, quantum computing and other innovative technology during a Silicon Valley roundtable on Friday.

It was the latest effort by the Asian neighbors to improve ties, which had been in what Kishida called "deep difficulty" before he and Yoon embarked this year on a campaign to repair them.

The two have meet several times since a Camp David summit with U.S. President Joe Biden in August. Yoon and Kim met one on one and together with Biden on the sidelines of the Asia-Pacific Economic Cooperation (APEC) summit in San Francisco, which ended on Friday.

Concerned about a more aggressive China and the nuclear and missile ambitions of North Korea, Washington has been keen for its two key Asian allies to mend relations, frayed over issues such as the forced labor of Koreans under Japan's 1910-1945 colonization of the Korean Peninsula.

In addition to military and economic cooperation, Yoon and Kishida on Friday signaled work on science and technology would be a central to their relationship-building. Each spoke of the importance of technology sharing for "likeminded" countries.

Noting that innovations like quantum computing have national security implications, Yoon said cooperative development must take place with countries that have common values.

Kishida said he was looking forward to announcing a joint supply network with South Korea for carbon-neutral fuels such as hydrogen and ammonia.

"No single country can defend itself," Kishida said, "The same is true with technology – no one country alone can change the world."

The two leaders gave opening remarks from lecterns on opposite sides of the stage. They ended the event donning Stanford baseball caps, raising their fists and grinning together at the students and professors in the audience.

Both took note of the annual "Big Game" football match-up between Stanford and its San Francisco Bay Area rival, the University of California, Berkeley, set for Saturday.

"But for President Yoon and myself, this is the Big Game," Kishida said.

(Reporting by Ann Saphir; Editing by William Mallard)