The United States and Saudi Arabia have hamstrung global efforts to scrutinise climate geoengineering in order to benefit their fossil fuel industries, according to multiple sources at the United Nations environment assembly, taking place this week in Nairobi.

The world’s two biggest oil producers reportedly led opposition against plans to examine the risks of climate-manipulating technology such as sucking carbon out of the air, reflective mirrors in space, seeding the oceans and injecting particulates into the atmosphere.

Deeper analysis of the risks had been proposed by Switzerland and 12 other countries as a first step towards stronger oversight of potentially world-altering experiments that would have implications for food supply, biodiversity, global inequality and security. Some have been tried, but as yet none deployed at a scale that would affect the climate.

This call for caution was supported by the president of the assembly, Siim Kiisler, Estonia’s environment minister, “We need to talk about governance of geoengineering. We need an international agreement on this in the future. Just ignoring the issue does not help. We need to talk about it and how to govern those technologies in the future.”

But sources involved with the talks said the initiative was blocked, initially by the US and Saudi Arabia, then by Japan and other countries.

Once dismissed as reckless science fiction, geoengineering has risen up the political agenda of some nations as the climate crisis has become more apparent.

The petrochemical industry sees it as a way to justify further expansion of fossil fuel industries. Chevron, BHP and other high-emitting companies have invested in companies that are pushing ahead with experiments to pull CO 2 out of the air.

US academics at Harvard are also poised to conduct the biggest outdoor test of stratospheric aerosol injection, which simulates the cloaking effect of a volcano eruption. The researchers say this test, known as Scopex, will probably take place in New Mexico.

One of the leading US scientists behind such research, David Keith, published a paper this week claiming the risks of geoengineering are not as great as previously feared.

Opponents counter that earlier, more thorough studies show serious impacts on Asian monsoon cycles, African droughts, tropical cyclones and extreme temperatures. They want the UN to impose a moratorium on outdoor experiments using this form of technology.

“More than a scientific test, this is a political test. It’s a way to establish the technology,” warned Silvia Ribeiro of the industry watchdog ETC Group. “Stratospheric aerosol injection would cause huge imbalances in the climate. We think it will also exacerbate geopolitical unfairness.”

Many climate scientists argue such research is a distraction from proven methods of mitigating emissions through tree planting and a switch to renewable energy.

Jacqueline McGlade, professor of sustainable development at University College London, said she supported certain types of locally appropriate land-based geoengineering but was extremely concerned about efforts to play with the stratosphere. “If we mess around with particulate matter, it could potentially affect everyone. As far as atmospheric physics are concerned, we don’t know everything.”

Currently, the main prohibition on testing is the Convention on Biological Diversity, which the US is the only country not to have ratified. There are also provisions in the London Protocol, which forbids ocean seeding – another form of geoengineering, which aims to increase the capacity of sea water to absorb CO 2 . The question now is whether to strengthen the controls, by tightening rules and broadening oversight, or to narrow them down.

The US argues that geoengineering should be left to climate forums, such as the UN Intergovernmental Panel on Climate Change.

This week, consensus proved impossible. On Wednesday evening, the Swiss delegation withdrew their resolution and expressed regret that “some countries” were reluctant to move forward. “Our motivation was to get more information to inform discussions,” the head of the delegation Felix Wertli said. “Governance of geoengineering is an important topic today, and even more tomorrow. The topic is not off the table. It is the start of a further conversation.”

This was seen as a defeat for the “precautionary principle”, under which nations are supposed to put safety first when faced with uncertain but potentially catastrophic risks. Campaigners warned future debates on the subject are now more likely to focus narrowly on science and politics, rather than other species, food supply, water use, inequality and peace.

“It is regrettable that efforts to strengthen existing UN governance on geoengineering met with resistance from a handful of high-emitting oil-producing countries,” said Lili Fuhr of the Heinrich Böll Foundation. “This task is now more important than ever as we see real-world experiments and public support for these technologies growing in exactly those countries, like the USA and Saudi Arabia, that were blocking progress on this issue this week in Nairobi.”

This was not the only agenda item in Nairobi that Trump administration diplomats were accused of watering down; they were also accused of undermining efforts to ensure strong environmental governance. “They are trying to remove all targets and timelines,” said one senior delegate.

An ambitious Indian resolution to phase out single-use plastics by 2025 has been diluted to resolving to “significantly reduce” them by 2030, said another delegate. The US was supported by Brazil and at least four other countries in pushing back the deadline and making the language more vague.

On marine waste, a Norwegian proposal to build an effective global strategy for dealing with plastics that enter the oceans has also met with resistance from the US. “They want to postpone measures so they can protect their industry,” said an ambassador from a large developing country.

Approached by the Guardian, a US official denied his country was playing an obstructionist role.

This could prove to be the last time the UK is part of the European Union delegation at an international conference, and there is speculation that after Brexit the British position may be realigned with the economy-first, environment-second approach of Washington.