More than 8 million tons of plastic are dumped into the world’s oceans every year, equivalent to a garbage truck’s worth every minute, and by 2050 there will be more plastic in the oceans by weight than fish, scientists predict.

But agreeing on a common approach to the problem has proved problematic, with the United States blocking demands to set a global target to significantly reduce or phase out single-use plastics.

“Marine litter and especially marine plastic litter and microplastics, is a matter requiring urgent attention given its adverse impacts on marine ecosystems, livelihoods and industries including fisheries, tourism and shipping, and potentially on human health,” environment ministers from the G-20 said on Sunday.

The ministers said they were “determined to drive measures to resolve this issue,” while also noting that “plastics play an important role in our economies and daily lives.”

But they failed to agree on any firm, shared commitments, talking only of “encouraging voluntary actions” by G-20 members “in accordance with national policies.”

The issue of marine plastic pollution has become an increasing hot diplomatic topic over the past year, and there have been calls for collective action at G-20, Group of Seven and United Nations forums.

The European Union aims to phase out single-use plastics by 2030 and make all packaging reusable or recyclable.

Countries from all over the world pledged at a United Nations Environment Assembly in Nairobi in March to significantly reduce the manufacture and use of single-use plastics by 2030 – apart from the United States, which spent two weeks in Nairobi watering down the proposals before finally signaling its rejection of the declaration on the final day.

Instead, the Trump administration blames the problem on Asian countries where huge amounts of plastic is being washed along rivers and into the sea.

“Sixty percent of the marine plastic waste comes from six Asian countries, and 80 percent of the waste comes from four rivers internationally,” Environment Protection Agency Administrator David Wheeler told reporters in Kariuzawa. “We know where those problems are, and we can do a lot to address that.”

One widely quoted study found that China was the largest direct source of marine plastics litter, with Indonesia also a significant contributor. Wheeler said it would be wrong to focus exclusively on single-use plastic, at the expense of dealing with waste management issues.

But environmentalists say the Trump administration’s argument ignores the fact that the United States has long been the world’s biggest exporter of plastic waste to poorer countries, with dire environmental consequences.

It also glosses over the role of U.S. corporations in selling plastics and products packed in non-recyclable plastic to developing countries, often in small single-use sachets.

“The United States is very, very beholden to industry interests,” said Christoper Chin, executive director of COARE, a San Francisco-based group specializing in protecting the oceans.

COARE and many other environmental groups such as the World Wildlife Fund for Nature and Greenpeace are calling for a legally binding treaty to be drawn up to curb marine plastic pollution. They argue that an essential element of such a treaty has to a shared global commitment to significantly reduce or phase out single-use plastic.

“We believe that all countries should take responsibility but also that corporations should take responsibility,” said Sirine Rached at the Global Alliance for Incinerator Alternatives.

“What has been happening for some years is basically global plastic waste dumping from the Global North to the Global South, under the guise of legitimate recycling,” she said. “To put the blame on these Global South countries we really think is unacceptable.”

On Sunday, the G-20 issued an “implementation framework for actions on marine plastic litter,” vowing to “promote a life-cycle approach” to urgently reduce plastic littler discharge into the oceans, through waste management, cleanups, innovative solutions and international cooperation.

It also pledged to prevent and reduce plastic waste generation and promote sustainable consumption, to share information, scientific knowledge and best practices among G-20 nations, and “encourage” the development of global monitoring of marine litter.

Japan, chairing the G-20, wants to make marine plastic litter one of the key themes when leaders from the grouping meet for a summit in Osaka at the end of this month, with Prime Minister Shinzo Abe vowing to “build a shared sense that it takes a worldwide commitment not to increase but to reduce plastics flowing into the seas.”

But critics say Japan is not moving fast enough to deal with its own massive consumption of plastics to cast itself as a true leader on the issue.

At this weekend’s meeting, faced with disagreement between the European Union and the United States, officials admitted it was impossible to get more concrete commitments or stronger language.

“Each country has their own view,” Hiroshi Ono, deputy director-general of global environmental affairs in Japan’s Ministry of Environment told reporters. “It is very difficult to have too strong wording.”

But environmentalists said what emerged was too vague to deal with an urgent crisis.

“It is totally disappointing,” said Yukihiro Misawa, plastics policy manager for WWF Japan. “Japan has set a low bar in order to gain consensus.”