Japan's Fisheries Agency says that of the 88 member nations in the International Whaling Commission, 40 could be listed as approving of whaling.
The agency placed the IWC's members into two groups of approving and disapproving of whaling, based on their past voting behavior in IWC activities and other data.
Norway and Iceland have been conducting commercial whaling, while in the IWC.
Both nations say they only hunt whales that aren't endangered and only as long as the practice is sustainable.
Agency officials note that Russia, Denmark and the Caribbean state of Saint Vincent and the Grenadines approve of indigenous people catching whales as a means of sustenance.
Canada and Indonesia, both non-IWC member states, engage in commercial whaling.
Agency officials say they classify 48 IWC member nations as anti-whaling. They include most European countries as well as the United States and Brazil.
But the US allows indigenous Inuits in Alaska and others to hunt whales. They have caught more than 1,000 between 2013 and 2018.