BRUSSELS (Reuters) - EU nations refused to back a limited extension of the herbicide glyphosate’s use on Monday, threatening withdrawal of Monsanto’s Roundup and other weed-killers from shelves if no decision is reached by the end of the month.

Weedkillers including Monsanto's Roundup are displayed for sale at a garden shop at Bonneuil-Sur-Marne near Paris, France, June 16, 2015. REUTERS/Charles Platiau

Contradictory findings on carcinogenic risks have thrust the chemical into the center of a dispute among EU and U.S. politicians, regulators and researchers. Citizen and environmental groups have urged governments to exercise caution.

The EU executive had offered a 12- to 18-month extension to allow time for further scientific study by the European Chemicals Agency (ECHA), in hopes of allaying health concerns. Its earlier proposal to renew the glyphosate license for up to 15 years had failed to win support in two meetings this year.

The compromise proposal failed to win the qualified majority needed for adoption, an EU official said, adding the European Commission will discuss the issue at a meeting on Tuesday.

Seven member states abstained and 20 backed the proposal, a German environment ministry spokeswoman said. Only Malta voted against, diplomats said.

Without a majority decision that meets the required percentage of total EU population, the EU executive may submit its proposal to an appeal committee of political representatives of the 28 member states within a month. If there is again no decision, the European Commission may adopt its own proposal.

Monsanto on Monday defended the safety of its widely used herbicide, and said glyphosate’s license should be renewed for the full 15 years.

“Further delays in this process represent a significant deviation from the EU regulatory framework and set a concerning precedent for other active substances,” Philip Miller, Monsanto’s vice president of global regulatory and government affairs, said in a statement.

Monsanto has not ruled out a legal appeal if approval lapses after June 30, requiring a six-month phase-out of glyphosate-containing products. The industry lobby has criticized the regulatory uncertainty.

The controversy hangs over German chemicals group Bayer’s $62 billion offer in May to buy U.S. seeds company Monsanto. Germany was among states which abstained on Monday and has opposed Monsanto’s genetically modified seeds.

Glyphosate use is key for Monsanto in the United States and Brazil, where the U.S. company depends on sales of genetically modified corn and soybean seeds that can resist the widely used weed killer.

In Europe, sale and use of such seeds faces strong opposition and plays virtually no role in commercial farming. But an EU refusal of a new glyphosate license could signal stricter regulation of the broader agricultural chemicals industry.

It would also hit Monsanto’s bottom line: If the EU were to halt glyphosate sales, the company could see earnings reduced by up to $100 million as its premium branded Roundup product is diverted to the generic market, said Bernstein senior analyst Jonas Oxgaard.

SMELLING GAS

Quashing the licenses in Europe might further embolden glyphosate foes elsewhere.

“With this decision all they do is cast doubt ... and create fear and confusion amongst Europe’s consumers,” Graeme Taylor of the European Crop Protection Association said.

Environmental and citizen campaign groups have called for an EU-wide ban in the absence of scientific certainty.

“Extending the glyphosate license would be like smelling gas and refusing to evacuate to check for a leak,” Greenpeace EU food policy director Franziska Achterberg said in a statement.

The prospect of a European ban could complicate EU-U.S. trade talks.

The U.N.’s Food and Agriculture Organization (FAO) and World Health Organization (WHO) said in May glyphosate was unlikely to pose a risk to people exposed to it through food.

The finding matches that of the European Food Safety Authority (EFSA), an independent agency funded by the European Union, but runs counter to a March 2015 study by the WHO’s Lyon-based International Agency for Research on Cancer (IARC).

That agency said the chemical was probably able to cause cancer and classified it as a ‘Group 2A’ carcinogen. It assessed whether the substance can cause cancer in any way - regardless of real-life conditions on typical levels of human exposure or consumption.