Japan plans to make public some testimony denying that Koreans were forced to work under harsh conditions during World War II at what is now a UNESCO World Cultural Heritage site, government sources have said.

The controversial move could draw an angry rebuke from Seoul, which maintains that Korean workers were forced to toil in the Hashima Coal Mine off Nagasaki, on what is now known as Gunkanjima (“Battleship Island”), when the Korean Peninsula was under Japanese colonial rule between 1910 and 1945.

When the island was listed as a World Cultural Heritage site in 2015, Tokyo promised Seoul it would exhibit the history of Koreans forced to work there. Japan may continue to collect more testimony, potentially including acknowledgements of forced labor.

The sources said the testimony will be exhibited at an information center for Japan’s World Cultural Heritage Site that the government plans to open in Tokyo by 2019.

The move comes as the two Asian neighbors seek to bolster cooperation in addressing North Korea’s nuclear and missile threats, and as Japan hammers out the details of hosting a trilateral summit also involving Beijing in the near future.

The testimonies denying forced labor are part of 200 hours of video recordings of around 60 former islanders, including Korean residents in Japan.

One says “I believe Korean people were not forced to do dangerous work,” while another says “Japanese and Koreans were treated the same way in the coal mine.”

It was unclear if those two statements were made by Japanese or Korean residents in Japan.

All of the witnesses live in Japan, though the government is considering compiling testimony from former mine workers now living in South Korea, the sources added.

Tokyo has told UNESCO that it will collect former islanders’ testimonies and other materials to exhibit, the sources said.

South Korea had initially opposed adding the island to the World Cultural Heritage list under “Sites of Japan’s Meiji Industrial Revolution,” saying Koreans were forced to work at some sites. It later dropped its opposition on the condition that Japan publicly acknowledge that Koreans were coerced to work at some of the sites.

Despite that deal, Tokyo and Seoul have remained at odds over the definition of forced labor.