The US will support a global treaty calling for a reduction in how much plastic is produced each year, according to US officials, signalling a policy shift as countries race to reach a final agreement to curb the pollution increasingly found to be harmful to human health.

The fresh backing for more limited production of plastic from one of the world’s largest producers will boost the prospect of the UN being able to unveil a landmark treaty to manage waste by the end of this year when a final round of negotiations is due to take place in South Korea, just two weeks after the November US presidential election.

In UN talks earlier this year, the US was aligned with China and Saudi Arabia in resisting the inclusion of plastic production controls in a treaty, instead calling for a focus on recycling and re-use.