The National Tax Agency is considering defining "Japanese sake" as a home-brewed alcoholic drink made from Japanese-grown rice in order to differentiate it from foreign-brewed sake, according to sources.

The agency is mulling the definition to improve the brand of Japanese sake and help give a boost to its overseas sales, the sources said Tuesday.

Members of the World Trade Organization have agreed to the use of "geographical indications" for products whose origins are linked to their quality.

As there has been no clear definition of sake, the agency is planning to decide by the end of this year on the geographical indication of Japanese sake.

Amid a global Japanese food boom in recent years, moves to produce sake are spreading abroad.

If the envisaged geographical indication is approved by other countries, Japan can ask them not to sell foreign-made sake as Japanese.

A Japanese sake specialist welcomed the proposed move, saying it is worthy of "big applause."

Toshie Hiraide, who works to promote Japanese sake internationally for domestic sake promotion group Sake Samurai, said the change would push forward a national discussion to encourage Japanese sake brands internationally.

The move is a very important step "for bucking up the value of Japan-made products," she said, especially given that domestic sales are declining.

But Japanese-made sake is becoming increasingly popular overseas. The value of exports of Japanese sake increased to ¥11.5 billion in 2014, setting a record for the fifth consecutive year, according to statistics provided by the National Tax Agency.

The top three importers are the United States, Hong Kong and South Korea.

The volume of sake exports has also broken the record for five consecutive years. Some 16,316 kiloliters were sent overseas in 2014, according to the agency.