The EU on Wednesday postponed a vote on proposals to renew the licence for the controversial weedkiller glyphosate, which critics say causes cancer and which the European Parliament wants banned in five years' time.

A panel of experts from the EU's 28 member states met behind closed doors to consider plans to extend the European licence for glyphosate -- the key ingredient in best-selling weedkiller Roundup -- when it expires on December 15.

The European Commission, the bloc's executive arm, had originally recommended approving the herbicide's use for another 10 years but offered a watered-down alternative of five to seven years amid growing uproar over the alleged dangers of its use.

But at the end of the meeting no vote was taken, the commission said, amid growing unease among several European Union states about the possible risks to human health posed by the herbicide.

"The commission took note of the positions of the different delegations of member states, upon which it will now reflect, and will announce the date of the next meeting shortly," the commission said in a statement.

It said the aim was to find "a solution that enjoys the largest possible support" among EU states and ensures a "high level of protection" of health and the environment.

The Danish environment ministry tweeted that it had been "impossible to reach an agreement" on the commission proposal.

Glyphosate critics, led by environmental campaigners Greenpeace, are calling for an outright ban in Europe and on Monday activists handed the EU a petition signed by more than 1.3 million people backing such a move.

They point to a 2015 study by the World Health Organization's (WHO) International Agency for Research on Cancer that concluded it was "probably carcinogenic".

One of Europe's heaviest users France, whose government has said it wants to phase out the herbicide, said along with Italy and Austria it would vote against renewing the glyphosate licence for 10 years.

On Wednesday Belgium joined the ranks of opponents, telling AFP it wanted to see glyphosate phased out.

- 'Political roulette' -

The European Parliament on Monday said glyphosate should be renewed only until 2022 and banned thereafter, calling for a halt to non-professional use of the herbicide when its current licence expires on December 15.

Even if Brussels renews the glyphosate licence, member states will still be able to ban individual products such as Roundup on a national basis.

The herbicide's fate is a key issue in German coalition talks, where Chancellor Angela Merkel is trying to thrash out a deal with the Greens and the pro-business Free Democrats.

"The glyphosate subject which is already important...  will have to be discussed" by the three sides, said German government spokesman Steffen Seibert.

Greenpeace said the failure to reach agreement on Wednesday showed there was growing opposition to extend approval for the herbicide.

Today the commission failed for the fifth time in a row to get sufficient support from European governments to renew glyphosate's licence. The tables are turning and unless the Commission backs a ban, it will continue to fail," the campaign group's EU food policy director Franziska Achterberg said in a statement.

Monsanto, the US agro giant that makes Roundup, insists glyphosate meets the standards required to renew its European licence.

The European Food Safety Authority and the European Chemicals Agency, both say glyphosate is unlikely to cause cancer in humans, in line with a 2016 review carried out by WHO experts and the UN Food and Agriculture Organization.

Graeme Taylor of the European Crop Protection Association said it was "disappointing" the EU had still not reached a decision on an issue that has been dragging on for more than two years.

"If member states followed science we would have had a 15-year decision last year," he said.

"Science is now being traded away in a high-stakes game of political roulette to decide how long an approval the substance should be granted."