The vote, scheduled to take place at a meeting of EU countries' environment ministers on Monday in Brussels, was called off after Hungary said it would no longer back the policy - wiping out the already-slim reinforced majority of countries in favour and leaving ministers struggling to decide their next steps.

The nature law is the latest EU environmental policy to come under fire as policymakers try to respond to months of angry farmers' protests over complaints including strict green EU regulations. The EU has already weakened numerous green rules to attempt to quell the protests.

"The agricultural sector is a very important sector, not only in Hungary, but everywhere in Europe," Hungary's state secretary for environment Aniko Raisz told reporters. She said Hungary's concerns included the cost of implementing the law.

EU countries and lawmakers agreed a deal on the law in November, which was supposed to be final. Cancelling a policy at this late stage of EU lawmaking is highly unusual.

EU environment commissioner Virginijus Sinkevicius said shelving the law would send a "disastrous signal" about the EU's credibility, especially after the bloc pushed other countries in U.N. negotiations to back stronger targets to protect nature.

"We are fooling ourselves if we pretend that we can win our fight against climate change without nature," Sinkevicius said.

Some EU diplomats said that countries had already substantially weakened the law during negotiations, and suggested Budapest's move was purely political, rather than a specific complaint about the policy's content.

Opposed to it are Hungary, Italy, the Netherlands and Sweden. Austria, Belgium, Finland and Poland intend to abstain in the vote.

Any one of those eight countries changing position could allow the law to pass. The rest of the EU's 27 member states support the policy.

"We can't give up. I urge member states to reach a breakthrough," German Environment Minister Steffi Lemke said.

Spanish climate minister Teresa Ribera said it would be a "huge irresponsibility" to reduce efforts to tackle worsening nature loss and climate change.

"We cannot ignore the situation in the farming sector," Italy's deputy environment minister Vannia Gava said.

EU countries' environment ministers were discussing their next steps on Monday afternoon.

The law would be among the EU's biggest environmental policies, requiring countries to introduce measures restoring nature on a fifth of their land and sea by 2030.

Its aim is to turn around the 81% of Europe's natural habitats that are classed as in poor condition. But the policy has faced a backlash from some governments and lawmakers concerned it would impose burdensome rules on farmers, or clash with other industries.