Tourists and local residents disembark from a boat coming from nearby Nusa Penida island as plastic trash pollutes the beach in Bali, Indonesia on Tuesday.Photo: VCG

The United Nations is to launch formal negotiations on Wednesday for a global treaty to address a plastic trash "epidemic" that supporters say is a historic moment for the planet.

The UN Environment Assembly (UNEA), convening in Nairobi, is poised to adopt a resolution creating an intergovernmental committee to negotiate and finalize a legally binding agreement by 2024.

The amount of plastic trash entering the oceans is forecast to triple by 2040, and governments have been under pressure to unite behind a global response to the crisis.

The framework for a comprehensive treaty has been approved by UN member states, including major plastic producers like the US and China, according to sources close to the negotiations.

Officials say it gives negotiators a broad and robust mandate to consider new rules that target plastic pollution from its birth as a raw material to its design, use and safe disposal.

This could include limits on making new plastic, which is derived from oil and gas, though policy specifics will only be determined during later talks. The mandate provides for the negotiation of binding global targets with monitoring mechanisms, the development of national plans and financing for poorer countries. 

Negotiators also have the scope to consider all aspects of pollution - not just plastic in the ocean but tiny particles in the air, soil and food chain - a key demand of many countries.

"We are 100 percent happy with the outcome," said Ana Teresa Lecaros, director of environment in the foreign ministry of Peru, a country that co-signed one of the draft resolutions. Inger Andersen, head of the UN Environment Programme, said a plastics treaty would be "one for the history books" and the most important pact for the planet since the Paris climate agreement. 

The rate of plastic production has grown faster than any other material and is expected to double within two decades, the UN says.

But less than 10 percent is recycled, with most winding up in landfill or oceans.

By some estimates, a garbage truck's worth of plastic is dumped into the sea every minute. "Plastic pollution has grown into an epidemic of its own," said Norway's climate and environment minister, Espen Barth Eide, who chairs UNEA.

He said he was "quite optimistic" about bringing down the gavel on a strong resolution in Nairobi.

Environment groups are also buoyed by the outcome of the talks, but like officials and diplomats, caution that the strength of any treaty will only be determined by rigorous negotiations to come. 

The first round of discussions is set for May, according to sources involved in the process.