(Adds reaction from Ecuador, paragraph 8)

BOGOTA, Feb 9 (Reuters) - Colombia halted aerial spraying of chemicals on drug crops along its border with Ecuador on Friday after Quito renewed charges that the U.S.-backed anti-narcotics program was harming residents and farms.

Tensions between the Andean neighbors heated up in December after Colombia restarted the spraying of herbicides it says are not only safe but vital to combating the coca leaf -- the raw material used to manufacture cocaine.

Colombian President Alvaro Uribe, an ally to Washington, and Rafael Correa, his leftist counterpart in Ecuador, agreed in January to allow Ecuador to monitor spraying.

But Ecuador still says it could sue Colombia, the world's top cocaine producer, over the use of the herbicides.

"Colombia will now start manual eradication and end the fumigation phase so there should be good faith to put into action the agreement between the two presidents," Foreign Minister Maria Consuelo Araujo said in a statement.

She said 1,200 workers would sweep southern Putumayo and Narino provinces, where leftist rebels and militias fight over rich coca leaf territory close to the border with Ecuador.

Ecuador's government recalled its ambassador last year in protest over the spraying.

But Foreign Minister Maria Espinosa said on Friday that Colombia's decision opened up space for more dialogue between the two governments.

Colombia has received around $4 billion in U.S. aid since 2000 to help fight the drug trade that fuels its four-decade internal conflict, Latin America's longest-running left-wing insurgency.

Colombia says the U.S.-backed fumigation program is the only way it can counter coca production in remote areas where guerrillas are still fighting government forces.

Correa, who echoes Venezuelan President Hugo Chavez's criticism of U.S. policies in the region, wants Colombia to halt all fumigation and conduct more studies on the effects of the herbicides used.

Critics of U.S. policy say coca leaf production is about the same as when Washington began its Plan Colombia program.

The White House's anti-drug office said 144,000 hectares of coca were detected in 2005, enough to produce more than 500 tonnes of pure cocaine. (Additional reporting by Alexandra Valencia in Quito)

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