The expected closing session of the UN talks was postponed until Thursday evening, with an overnight session looking increasingly likely.
At least 180 countries agree that plastic pollution - in oceans, mountains, the air and now human bodies - poses a major threat.
However, they disagree on what to do about it.
More than 100 members of the High Ambition Coalition, including the European Union and dozens of countries in South America, Africa and Asia, are calling for plastic production to be limited to sustainable levels.
They also want to phase out so-called "single-use" plastic products such as cups and cutlery, and promote reusable plastic products and a circular economy in which the raw materials of a waste product are recycled and reused.
Oil-producing countries including Saudi Arabia, Iran and Russia call themselves the "like-minded group".
They want to focus on limiting plastic waste, rather than limiting production.
Plastic is largely made from oil products.
However, the UN gave itself the mandate in 2022 to agree to a treaty that covers the entire life cycle of plastic, from production to design and waste management.
On Wednesday, conference chair Luis Vayas Valdivieso presented what he called a compromise paper, which was met with outrage from dozens of countries who said he had removed virtually all ambitious or controversial targets from the text, including Article 6 on production limits.
Hardly anyone saw the paper as a basis for negotiation for a final text, with even the oil-producing countries dissatisfied.
Saudi Arabia, speaking on behalf of the like-minded group, criticised paragraphs that recommended research into alternatives to plastic or liability for plastic producers.
The countries have been negotiating for three years already.
Any agreement would take years to implement due to the necessary ratifications.
Plastic pollutes the oceans and the environment, kills fish and other living creatures and endangers human health.
Tiny particles are increasingly being found in human organs including the brain.
According to studies, nano and microplastic particles impair the immune system and promote inflammation.
Germany's environment ministry said global plastic production increased sevenfold between the 1970s and 2020 to 367 million tonnes per year, and could reach almost 600 million tonnes by 2050 if no measures are taken.
It said a total of 8.3 billion tonnes of plastic have been produced to date, 6.3 billion tonnes of which have become waste, most of which ending up in landfill.
According to estimates, 152 million tonnes of plastic waste have accumulated in rivers and oceans worldwide.
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