The controversial weedkiller glyphosate, which is used by Monsanto in its herbicide Roundup, is "unlikely" to cause cancer, a United Nations finding said Monday, in a blow to critics who have called for its ban.

Last month, the European parliament urged the EU to only approve glyphosate's use for seven years instead of 15 as requested by the bloc's top regulator amid fears that the product could be carcinogenic.

A review carried out by pesticide experts from the World Health Organization and the Food and Agriculture Organization said "glyphosate is unlikely to pose a carcinogenic risk to humans from exposure through the diet."

That appeared to contradict a March 2015 finding from the WHO's International Agency for Research on Cancer (IARC) which said glyphosate "probably" caused cancer.

WHO said the two findings were not contradictory.

It said the IARC finding was based on whether glyphosate could potentially pose any "hazard" to human health, including in extremely high levels of exposure.

The joint WHO/FAO panel reviewed all available evidence to assess specific risk to people consuming limited quantities of the chemical through food.

The earlier WHO finding was cited by activists led by Greenpeace who called for the ingredient's outright ban.

In March, regulators from the 28 EU members states, in addition to the European Commission, delayed their decision on rolling over the approval for glyphosate amid fierce lobbying from both sides of the issue.

The EU pesticides committee is set to meet on Wednesday to decide on whether to extend glyphosate's licence.

The latest UN findings could tip the decision in favour of agriculture giant Monsanto, which has fought hard to secure market approval for its key product.

Among major EU member states, France and Austria have expressed opposition to glyphosate, while Britain and Germany are said to support its use generally.