The conservation group WWF urged Japan on Thursday to ban in principle all ivory trade within the country by 2020, saying its domestic market undermines international efforts to abolish illegal trade in ivory.

The United States, China and other countries have taken steps toward closing their domestic markets to protect endangered African elephants. But Japan insists on maintaining its own, arguing its domestic trading is unrelated to poaching.

After receiving a written request from the WWF, the Environment Ministry indicated its intent to strengthen measures to stop the smuggling of ivory by working with police and customs officers. The ministry did not make a clear response to the request for the closure of the domestic market, according to the WWF.

The WWF said more than 2.4 tons of ivory was unlawfully exported from Japan to China and elsewhere between 2011 and 2016.

While Japan amended its conservation law last year to tighten control over the market, by requiring ivory dealers to register with the government, the WWF said such a measure does not resolve the pressing issues involving ivory.

Fearing the illegal export of ivory could increase as the number of tourists to Japan rises ahead of the Tokyo Olympic and Paralympic Games in 2020, the WWF also requested the Japanese government ban online trade in ivory.

In 2016, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, or CITES, adopted a resolution calling on all signatories to close their domestic ivory markets in the face of the mass slaughter of elephants.

Japan, a party to CITES, has since imposed stricter rules but left its ivory market open, arguing that ivory products being traded in the country were imported before international regulations came into force and that related businesses are properly controlled.