Japan's efforts to register its Sado mine, a site linked to wartime forced labor, as a UNESCO World Heritage site next year appears exceedingly unlikely.

In a Thursday press conference, the country's culture minister Shinsuke Suematsu said that UNESCO did not proceed with deliberations after the secretariat found the relevant recommendation filings inadequate.

Japan asked the agency to reconsider, sending a letter to the director-general and dispatching an official to Paris, but the organization ultimately declined to take another look at the submission.

The minister said Tokyo confirmed that the secretariat's decision will not change, adding that another recommendation form in accordance with a new format introduced this year, will need to be resubmitted.

The Japanese government plans to resubmit the document in question, eyeing heritage designation in 2024, a year later than it hoped for.

Japan's Kyodo News earlier reported that UNESCO has pointed to the lack of data indicating the scope of the Sado mine complex.