KUALA LUMPUR: Malaysia will return a container of plastic trash en route from the United States as it violates new U.N. rules governing hazardous waste, the environment ministry said on Wednesday, one of the first signs of the regulations being enforced.

Two years ago, more than 180 countries agreed to ban hard-to-recycle plastic waste trade in an attempt to stop rich countries dumping trash in the developing world, where it often ends up polluting the local environment and the ocean.

The new restrictions, which come under the Basel Convention, a United Nations treaty that polices the trade in hazardous waste, came into force in January.

Signatory countries can now only trade plastic waste if it meets certain low-contamination criteria - which means it is clean, sorted and easy-to-recycle - or if the exporting country gets prior consent from the importing country.

Mohamad Khalil Zaiyany Sumiran, the environment ministry's spokesman, told Reuters a shipment was on its way from the United States, that authorities have said did not meet that criteria or have prior approval to be imported into Malaysia.

"After investigations, Malaysia will send back the container to the origin country," said Mohamad Khalil, adding that it was unclear when the shipment would arrive.

Malaysia's environment minister Tuan Ibrahim Tuan Man had said in a statement on Saturday that authorities would bar the container, which was shipped from Los Angeles, California on March 14.

The United States, which produces more plastic waste per capita than any other country, is the only major nation not to have ratified the Basel Convention and is not bound by its rules. However, under the treaty, Malaysia cannot accept prohibited plastic waste from the United States.

Malaysia, which became the leading destination for the world's plastic trash after China banned imports in 2018, has returned thousands of tonnes of plastic scrap since then.

The Basel Action Network, an NGO, said this month that contaminated plastic waste trade was still flowing despite the new U.N. rules, highlighting the high volume being shipped from the United States to Malaysia.