South Korea informed Japan and the United States via diplomatic channels before announcing earlier this week its agreement with North Korea to restore inter-Korean communications lines, Japanese and South Korean diplomatic sources said Thursday.

The advance notice about the Tuesday announcement signals the government of President Moon Jae-in placing importance on cooperation with the United States and Japan on North Korean issues despite having frosty ties with Tokyo over wartime labor and other issues.

The U.S. administration of President Joe Biden is working to restore relations with its allies that frayed under his predecessor Donald Trump's administration and has attached importance to the trilateral framework involving the United States and its key Asian allies.