The drive against coca could lead to clashes with rebel groups

The 2,000 troops, along with 1,500 police officers, will guard hundreds of farmers as they pull up the plants in the Sierra Macarena National Park, 170km (100 miles) south of Bogota.

The operation is expected to take around three months.

In December, rebels killed 29 soldiers working to destroy coca near the park.

President Alvaro Uribe vowed to wipe out coca in the region after the attack, which was blamed on the country's main rebel group, the Revolutionary Armed Forces of Colombia, or Farc.

Rebel funding

The illegal drugs trade is a key source of funding for the Marxist insurgent group.

Rebels have moved into national parks to grow coca because environmental concerns block chemical spraying within them.

For "Operation Macarena", 900 farmers have been employed to pull the plants up by hand from around 4,600 hectares of land inside the park.

Troops will guard the farmers and search for and destroy infrastructure related to the drugs trade within the park. The army will also provide support for the operation.

Gen Jorge Daniel Castro, the National Police chief in charge of the operation, said it was risky work which could lead to clashes with the Farc.

"It's going to be very difficult because this is the Farc's territory," he told The Associated Press.