Japan is withholding its annual contribution to UNESCO in an apparent protest over files on the Nanking Massacre being added to the organization’s Memory of the World Register last year.

The government usually submits its contribution in April or May each year after the budget for the year has been passed, in compliance with UNESCO’s request.

This year’s Japanese share was calculated at 3.85 billion yen ($37 million). Tokyo is effectively the biggest contributor.

The revelation over the stalled payment came at a briefing on Oct. 13 for the ruling Liberal Democratic Party by Makita Shimokawa, director-general for cultural affairs at the Foreign Ministry.

“We have not paid a contribution (to UNESCO) yet for this year, although we paid soon after the budget was enacted in the past,” he said.

According to a Foreign Ministry official, Tokyo has not paid about 550 million yen it has promised at its discretion for a project to restore Angkor Wat, part of the UNESCO’s World Heritage-listed Angkor complex in Cambodia.

Koichiro Matsuura, former director-general of UNESCO, criticized the Japanese government for delaying the payment.

“It is poor judgment if Japan is delaying its contribution to make its point,” he said. “The stalled payment will impact UNESCO’s programs overall.”

In an interview with The Asahi Shimbun, the Foreign Ministry official said, “We will make an appropriate judgment after scrutinizing details of the UNESCO programs.”

The stalled payment revelation came after Japan expressed anger and threatened to cut off funding when historical documents about the Nanking Massacre were listed for UNESCO’s Memory of the World Register in October last year.

Japan blamed the registration system for not considering its views in the evaluation process.

Tokyo and Beijing dispute the number of Chinese killed by Japanese troops in Nanking, now called Nanjing, in late 1937 and 1938.

“We will consider our response, including the suspension of our share of contributions,” Chief Cabinet Secretary Yoshihide Suga said at that time.

Since then, Japan has been calling on UNESCO to let relevant parties voice their opinions during the evaluation process.

Each member nation of the United Nations Educational, Scientific and Cultural Organization is obliged to pay an assigned sum based on the ratio of its assessed contribution to the United Nations.

This year, Japan’s share was 9.6 percent, the second largest after the United States.

But Japan is effectively the biggest contributor as Washington, which is assigned 22 percent for 2016, has suspended its own payments since autumn 2011 in protest at Palestine joining UNESCO.

Japan is followed by China (7.9 percent), Germany (6.3 percent) and France (4.8 percent).

The UNESCO Memory of the World Register was established in 1992 with the aim of preserving historical documents.

For this year, groups from Japan, China, South Korea and other countries applied to have archives on wartime “comfort women” registered for the Memory of the World Register.

Comfort women are those who were forced to provide sex to Japanese troops before and during World War II.