Only an estimated nine percent of plastics ever produced are recycled. (File)

The Group of 20 major economies said they agreed a deal to reduce plastic waste that is choking the seas at a meeting in Japan on Sunday.

Under the agreement, G20 member countries committed to reducing plastic waste but gave little detail on how that would be done. They added that the steps would be voluntary and progress would be reported once a year, according to local media.

The Japanese government hopes to hold the first meeting in November, said newspaper Yomiuri Shimbun.

"It is great that we were able to make rules for all, including emerging and developing countries," Japanese environment minister Yoshiaki Harada said after the two-day meeting of the G20 environment and energy ministers' meeting.

Plastic pollution has become a global concern, particularly after bans imposed by China and other countries on the import of plastic waste from overseas.

Many countries, including Japan, have seen their waste pile up as a consequence.

Microplastics -- tiny pieces of degraded waste -- have attracted particular attention.

They absorb harmful chemicals, accumulating inside fish, birds and other animals, and are difficult to collect once in the water.

The framework agreed at the meeting in the central mountain resort of Karuizawa would be the first to reduce plastic pollution in the ocean involving not only rich nations but emerging economies as well.

"Legally binding" rules needed

The deal would be "the first step" to tackling plastic waste, Hiroaki Odachi of Greenpeace Japan said in a statement.

"However, it is insufficient to rely on countries' voluntary actions" to resolve the crisis, he said.

Only an estimated nine percent of plastics ever produced are recycled and campaigners say the only long-term solution to the plastic waste crisis is for companies to make less and consumers to use less.

"G20 countries should clearly announce that they will prioritise reducing generation of single-use plastics" along with recycling and reusing materials, Odachi said.

"Legally binding international rules with clear timelines and goals" are needed, similar to those in the Paris Agreement on climate, he added.

The 2015 Paris agreement commits signatories to efforts to cap global warming at "well below" two degrees Celsius (3.6 Fahrenheit).

Japan will demand businesses charge for plastic shopping bags next year to help reduce waste, said Japanese industry minister Hiroshige Seko on Saturday.

Many countries in the world already charge for single-use bags or ban them outright.