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.

Combined photo shows (from L) Japanese Foreign Minister Toshimitsu Motegi, U.S. Secretary of State Antony Blinken and their South Korean counterpart Chung Eui Yong ahead of a trilateral foreign ministerial meeting in London on May 5, 2021, on the sidelines of the Group of Seven foreign ministers talks. (Kyodo) ==Kyodo

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.

The Moon government appears to be responding in kind. "We believe South Korea will continue to work in concert with Japan and the United States going forward," a Japanese government official said.

South Korean media have reported that North and South Korea agreed last weekend to restore the lines that had been cut off by the North last year. The Japanese and South Korean diplomatic sources said Seoul reached out to Tokyo before Tuesday.

South Korea also said Tuesday that Moon and North Korean leader Kim Jong Un have agreed to improve inter-Korean ties, with Pyongyang's state-run Korean Central News Agency reporting that the leaders of the two Koreas "agreed to make a big stride in recovering the mutual trust and promoting reconciliation" by restoring the communication lines.

With North Korea keeping its borders closed due to the coronavirus pandemic, South Korea hopes to hold inter-Korean consultations online.

It remains to be seen whether the North would agree to hold substantive talks on such issues as the pandemic response and the possible rebuilding of an inter-Korean liaison office the North blew up in June last year.

Meanwhile, nuclear talks between the United State and North Korea remain stalemated after a summit meeting between Trump and Kim ended with no deal in February 2019. It is unclear whether the latest improvement in North-South ties could lead to a restart of the U.S.-North Korea talks.

Observers say North Korea could harden its stance once the United States and South Korea hold a joint military exercise in a scaled-down manner this summer despite the North Korean demand that it be called off. Pyongyang has denounced such exercises as preparations for invasion.

The North had cut off the inter-Korean communication lines in retaliation for anti-Pyongyang leaflets defector groups had sent over the border from the South by balloon.