The United States is trying to ease the tensions between its two Eastern Asian allies -- Japan and South Korea -- over Tokyo's export restriction of crucial high-tech materials to Seoul, the US Department of State said Thursday.

"Japan and South Korea are, of course, not only friends, they're allies ... we're going to do everything we can to pursue ways to strengthen our relationships between and amongst all three countries, both publicly and behind the scenes," US State Department Spokesperson Morgan Ortagus said at a press briefing.

"Both relationships are incredibly important. We all share, face shared regional challenges and priorities in the Indo-Pacific and around the world, and so we will continue to do that..." Ortagus added.

Last week, Japan tightened restrictions on exports of high-tech materials vital to produce semiconductors and display panels for TVs and smartphones to South Korea, citing "significant damage to the relationship of mutual trust," in response to a court ruling of South Korea over the issue of compensation for South Koreans forced to work for Japanese firms during World War II.

Last month, a South Korean appellate court upheld a lower court's order to a Japanese steelmaker to compensate the South Korean victims of forced labor during World War II.

The Seoul High Court ruled that Nippon Steel Corp. pay 100 million won (86,400 US dollars) in compensation each to the family members of the seven South Korean victims for their wartime forced labor without pay, according to local media reports.

The seven plaintiffs began the compensation suit in 2013, and a Seoul district court ruled in favor of them in 2015. For the past six years, all the plaintiffs passed away because of old age.

Japan, for its part, has claimed the rulings are not in line with international law and run counter to the foundation of friendly and cooperative relations between the two neighbors since the 1965 normalization of diplomatic ties.

It also maintains the matter of compensation for wartime labor was "finally and completely" resolved under the pact.

However, Japan maintained that the tighter export controls were not a retaliatory measure against South Korea, saying that Seoul had failed to show a satisfactory solution to the ongoing wartime labor dispute between both parties.

South Korea has condemned the move by Japan to tighten the export controls of materials and demanded Tokyo withdraw the measure, arguing that it runs counter to the spirit of fair trade.

Earlier on Thursday, the US State Department said that Secretary of State Mike Pompeo has spoken by phone on Wednesday with his South Korean counterpart, Kang Kyung-wha, on denuclearizing the Korean Peninsula and the state of US-Japan-South Korea ties.

During the phone talks, Kang said Japan's trade restriction moves would cause damage to South Korean companies and have a negative impact on world trade as well as US firms, according to South Korean Foreign Ministry.

South Korea will make efforts for the diplomatic resolution via dialogue with Japan, Kang was quoted as saying.

For his part, Pompeo expressed his "understanding" of South Korea's position, and agreed to continue cooperation to strengthen diplomatic communications between South Korea and the United States and trilaterally among South Korea, the United States and Japan, according to the ministry.

Japan's public broadcaster NHK reported that Japan and South Korea would hold talks in Tokyo on Friday at Seoul's request to discuss the export restrictions, the first of this kind since Japan implemented the measure last week.