The Mexican government has postponed a ban on the use of glyphosate, saying it has not found an alternative for the controversial weed killer.

The Latin American nation had planned to phase out the use of the herbicide — which critics say may cause cancer and threaten biodiversity — by April 1 of this year.

But "the conditions to replace the use of glyphosate in Mexican agriculture have not been fulfilled," the economy ministry said in a statement late Tuesday.

It said glyphosate will remain in use while the government continues to seek a "low-toxicity" alternative herbicide that would allow agricultural productivity to be maintained.

Glyphosate is one of the most widely used weed killers in the world, but the World Health Organization in 2015 classed it as "probably carcinogenic."

It is the main ingredient in weed killers including Roundup, made by German chemicals giant Bayer, which acquired the brand when it bought US company Monsanto in 2018.

Monsanto and Bayer have faced a wave of lawsuits in the US over allegations Roundup causes cancer.

The firm denies such claims but has paid out billions of dollars to settle legal disputes.