DEXTER FILKINS, MARK MAZZETTI and JAMES RISEN
KABUL, Afghanistan — Ahmed Wali Karzai, the brother of the Afghan president and a suspected player in the country’s booming illegal opium trade, gets regular payments from the Central Intelligence Agency, and has for much of the past eight years, according to current and former American officials.

The agency pays Mr. Karzai for a variety of services, including helping to recruit an Afghan paramilitary force that operates at the C.I.A.’s direction in and around the southern city of Kandahar, Mr. Karzai’s home.

The relationship between Mr. Karzai and the C.I.A. is wide ranging, several American officials said. He helps the C.I.A. operate a paramilitary group, the Kandahar Strike Force, that is used for raids against suspected insurgents and terrorists. On at least one occasion, the strike force has been accused of mounting an unauthorized operation against an official of the Afghan government, the officials said.

Mr. Karzai is also paid for allowing the C.I.A. and American Special Operations troops to rent a large compound outside the city — the former home of Mullah Mohammed Omar, the Taliban’s founder. The same compound is also the base of the Kandahar Strike Force. “He’s our landlord,” a senior American official said, speaking on the condition of anonymity.

Mr. Karzai also helps the C.I.A. communicate with and sometimes meet with Afghans loyal to the Taliban. Mr. Karzai’s role as a go-between between the Americans and the Taliban is now regarded as valuable by those who support working with Mr. Karzai, as the Obama administration is placing a greater focus on encouraging Taliban leaders to change sides.

A C.I.A. spokesman declined to comment for this article.

“No intelligence organization worth the name would ever entertain these kind of allegations,” said Paul Gimigliano, the spokesman.

“Hundreds of millions of dollars in drug money are flowing through the southern region, and nothing happens in southern Afghanistan without the regional leadership knowing about it,” a senior American military officer in Kabul said. Like most of the officials in this article, he spoke on the condition of anonymity because of the secrecy of the information.

Many chastise Karzai for being too docile in his dealings with corrupt governors and police chiefs and for maintaining ties for the country’s former warlords. But Karzai’s latest troubles are closer to home in nature: They center around allegations that one of his brothers is involved in drug trafficking. His younger brother Ahmed Wali Karzai is influential among the Popalzai, a Pashtun clan, in Karzai’s home province of Kandahar and is the chairman of the provincial council. It is believed the Ahmed Wali is also the head of a group involved in opium and heroin trafficking that smuggles drugs to the West through Iran and Turkey. Sources in security circles claim that he provides protection for drug transports in southern Afghanistan.