Government officials will inform executives of the ruling Liberal Democratic Party and junior coalition partner Komeito of the decision, they said.
It is extremely rare for Japan to withdraw from an worldwide organisation and the withdrawal could spark criticism from anti-whaling countries.
Authorities in Japan say eating whales is a piece of its way of life.
Japan has tenaciously asserted at IWC meetings that commercial whaling will be resumed for certain species whose populations are found to have sufficiently recovered based on scientific data obtained through whaling research.
In order to leave the IWC next year, Japan needs to notify the commission by January 1.
Two countries have withdrawn from the worldwide commission.
"Like other inter-governmental organisations, there is a withdrawal process and all member governments have the right to withdraw", Wells wrote, adding that Japan will have to give notice by January 1 if it wants to leave in 2019.
Japan has long towed the line with the IWC, which was established in 1948.
"We would like to wholeheartedly celebrate an end to Japan's whaling in the Southern Ocean, but if Japan leaves the International Whaling Commission and continues killing whales in the north Pacific it will be operating completely outside the bounds of international law", said Nicola Beynon, head of campaigns at Humane Society International in Australia.
Moreover, in 2014, the United Nations' International Court of Justice ordered that Japan stop its annual hunts in the Antarctic Ocean, because these hunts were clearly not for scientific purposes but rather for dinner menus.
"Under the rules of the International Whaling Commission, of which Japan is a member, there has been an international ban on commercial whaling since 1986 - though there is an exception for whaling conducted with ecological research in mind".
"Japan leaving could, on one side, tip the scales so that it could become an organization that deals with whale science and whale conservation". Supposedly they wanted to waters, however, only in the own coast, as well as in Japan's economic zone, to go on whaling.
Japan has previously threatened to quit the IWC, arguing that the moratorium was supposed to be a temporary measure and accusing the IWC of abandoning its original objective - managing the sustainable use of global whale stocks.