This undated photo shows a mine shaft built after the Meiji-era, in the Aikawa gold and silver mines in the Sado mine complex on the island of Sado, in Niigata Prefecture, Japan. (Yonhap)

An advisory body to a committee of the UN Educational, Scientific and Cultural Organization has deferred the nomination of a controversial former Japanese gold mine as a UNESCO World Heritage site, the Japanese government said Thursday.

The International Council on Monuments and Sites, one of the three advisories to the UNESCO World Heritage Committee, recommended "withholding" Sado mine's designation and demanded additional documents, the Japanese Agency for Cultural Affairs said.

The ICOMOS evaluation is regarded as having a decisive impact on the WHC's final decision on the inscription, set for July.

Japan has been pushing to inscribe the Sado mine, once the largest producer of gold in the 17th century, on the World Heritage list, but its bid has sparked protest from South Korea over the lack of its historical context as a site where thousands of Koreans were forced to toil during World War II, when Korea was a Japanese colony.

South Korea has called on Japan to "reflect the full history" of the Sado mine in its submission for the inscription, criticizing Tokyo for limiting the timeline specifically to the Edo era from 1603-1868 and excluding the modern history during which war atrocities were committed by the Japanese Imperial Army.

Seoul has stepped up efforts to deliver its position to the WHC and to ensure that its call for a full account of the mine's history is included in the ICOMOS recommendation.

South Korea's foreign ministry launched a task force in March to work on the issue, while continuing to consult with Japan through diplomatic channels, an official said.

South Korea has raised a similar issue over Japan's 2015 designation of Hashima Island, another site linked to the forced labor of Koreans. Despite its promise to build an information center detailing the history of the forced labor, Tokyo only highlighted the achievements of its industrial revolution.

In its recommendation in favor of Tokyo, ICOMOS had advised Japan to better reflect the whole history.

It is the second time for Japan to apply for the inscription of Sado Mine. Its previous submission in February 2022 was turned down due to incomplete documents. It resubmitted the application in January last year.

Under the rule, an inscription on the World Heritage list requires over two-thirds of the votes from the WHC member states, but it has been customary that the final decision is delivered upon consensus.

The WHC is due to announce its decision on the Sado mine at a meeting in New Delhi in late July.