Colombia on Wednesday said it would lift a decade-old ban on the use of glyphosate to kill coca crops, after US pressure to increase eradication efforts.
Glyphosate is commonly used as a weed-killer around the world, but was banned in Colombia in 2015 due to its potential harm to human health and the environment.
Police commander Carlos Triana said Wednesday that the authorities would again use the herbicide for non-aerial spraying of smaller plots.
The decision comes as the United States is pressing Colombia to step up the destruction of coca plantations in the face of record harvests and cocaine production.
President Gustavo Petro's leftist administration has resisted coca eradication and spraying, believing it hurts farmers more than cartels.
US President Donald Trump and Petro have also very publicly clashed on social media, trading barbs over forced deportations from the United States.
Against this backdrop, the White House will decide later this year whether it will blacklist Colombia for failing to curb drug production.
The measure could see the United States strip funding from a range of security and other projects, as well as delivering a significant blow to Colombia's international reputation.
The issue of glyphosate use and spraying more generally is said to have been discussed when Homeland Security Secretary Kristi Noem recently visited Colombia.
It is unclear whether Wednesday's announcement will be enough to dodge US blacklisting.
Police commander Triana said the chemical will not be used on coca plantations larger than 1.5 hectares.
It still faces opposition from many communities, who say it causes maladies and destroys legal crops.
The World Health Organisation believes glyphosate is "probably carcinogenic to humans."
But Petro is also under domestic pressure to tackle drug cartels and their lucrative but illegal revenue streams.
His "total peace" strategy has seen the military largely hold off fighting groups, hoping a truce would help bring them to the table.
Instead, the lull in pressure has allowed a plethora of armed groups to grow richer and more powerful.