Oct. 27 (Bloomberg) -- Three special agents with the U.S. Drug Enforcement Administration were among 14 Americans killed yesterday in helicopter crashes in Afghanistan, in one of the deadliest days for American forces in the country.

The agents, along with seven U.S. soldiers, were killed as their military helicopter withdrew following a firefight with suspected Taliban drug traffickers in western Afghanistan, NATO said in a statement.

Earlier in the day, two helicopters collided over southern Afghanistan, killing four U.S. soldiers, NATO said. The cause of both crashes is under investigation and the military said it doesn’t believe they were the result of enemy fire.

President Barack Obama, who is reviewing his war strategy in Afghanistan, paid tribute to the dead personnel. “They were willing to risk their lives, in this case, to prevent Afghanistan from once again becoming a safe haven for al-Qaeda and extremist allies,” Obama said yesterday at a naval air station in Jacksonville, Florida.

It was the heaviest single-day loss of life for American troops in Afghanistan since June 28, 2005, when 19 U.S. personnel died, 16 of them aboard a Special Forces MH-47 Chinook helicopter that was shot down by insurgents, the Associated Press reported.

The three special agents killed yesterday were the first deaths for the DEA since it began operations in Afghanistan in 2005 against the illicit opium trade funding the Taliban insurgency, AP reported.

Opium Trade

Afghanistan provides more than 90 percent of the world’s supply of opium, the raw ingredient for heroin. Revenue from the sale of illegal drugs is being used to finance terrorist training bases across the border in Pakistan, buy weapons and explosives for suicide bombings and import the chemicals needed for drug refining, according to the United Nations.

Taliban insurgents make as much as $160 million a year from opium compared with $100 million a decade ago, the Vienna-based UN Office on Drugs and Crime said in a report this month.

The helicopter carrying the DEA agents crashed after an operation with Afghan forces targeting a compound used by militants smuggling narcotics, according to the North Atlantic Treaty Organization.

More than a dozen enemy fighters were killed in an exchange of fire at the compound, according to the statement. Fourteen Afghan soldiers, 11 U.S. military personnel and one American civilian were injured in the crash.

Obama’s Review

U.S.-led forces and NATO are battling a resurgent Taliban in Afghanistan and Obama is weighing calls from U.S. General Stanley McChrystal for more U.S. troops to be deployed.

“I will never rush the solemn decision of sending you into harm’s way,” Obama told an audience that included about 3,500 servicemen and women at the air base in Jacksonville. “I won’t risk your lives unless it is absolutely necessary.”

Last week, former Vice President Dick Cheney said the White House “must stop dithering while America’s armed forces are in danger.”

Accusations of electoral fraud have complicated the president’s decision on whether to increase the number of troops in Afghanistan beyond the extra 21,000 he approved earlier this year. About 68,000 U.S. soldiers are currently in the country.

Afghans are scheduled to vote in a runoff election Nov. 7 between incumbent President Hamid Karzai and former Foreign Minister Abdullah Abdullah. The runoff was triggered by a partial recount of the Aug. 20 vote that found more than 1 million ballots, most of them for Karzai, were suspect, putting his tally below the more than 50 percent needed to win in the first round.

Karzai rejected Abdullah’s call to fire the country’s electoral commission chief before the runoff, saying he had done nothing wrong, the British Broadcasting Corp. reported. Abdullah said Azizullah Lodin had no credibility because he was appointed by the president, the broadcaster reported late yesterday.

To contact the reporter on this story: Ed Johnson in Sydney at ejohnson28@bloomberg.net.

Last Updated: October 26, 2009 20:20 EDT