The US Central Intelligence Agency (CIA) secretly carried out a decade-long operation to weaken Afghanistan`s opium production by dispersing modified poppy seeds over the country`s fields, according to a report.

The Washington Post reported Wednesday that the covert program, conducted between 2004 and 2015, aimed to degrade the potency of Afghanistan`s billion-dollar opium crop-a key source of income for the Taliban and other groups.

Citing 14 people familiar with the classified effort, the report said the CIA dropped specially developed poppy seeds that produced plants containing almost none of the chemicals used to make heroin.

The airdrops, initially using British C-130 aircraft, reportedly targeted the Afghan provinces of Nangarhar and Helmand.

The project, run by the CIA`s Crime and Narcotics Center, was authorized by a presidential finding from then-President George W. Bush and continued into the Obama administration, the paper said.

While the CIA did not immediately respond to the report, former officials told the newspaper the program was "tremendously expensive" and its results were mixed.​​​​​​​