Gimigliano, the CIA spokesman, declined to comment on the agency's financial ties to Afghan officials. "This agency plays an essential role in promoting American goals in Afghanistan, including security and stability," he said. "Speculation about who may help us achieve that is both dangerous and counterproductive."

The agency's approach has drawn criticism from others in the U.S. government, who accuse the CIA of contributing to an atmosphere in which Afghans are conditioned to extend their hands for secret payments in almost every transaction.

"They'll pay whoever they think can help them," the U.S. official said. "That has been the CIA attitude since 2001."

A second U.S. official defended the agency's activities and alluded to a simmering conflict within the U.S. government over the scope of American objectives in Afghanistan, and the means required to achieve those goals.

"No one is going to create Plato's Republic over there in one year, two years, or 10," the official said. "If the United States decides to deal only with the saints in Afghanistan, it's in for both loneliness and failure. That's the risk, and not everyone in our government sees it."

U.S. and Afghan officials said the CIA is not the only foreign entity using secret payments to Afghan officials to influence events in the country.

A prominent Afghan with knowledge of the inner workings of the palace said it operates a fund that rewards political allies with money that flows in from the Iranian government and foreign intelligence services as well as prominent Afghan companies eager to curry favor with Karzai. The source said the fund distributes $10 million to $50 million a year.

A U.S. official said Turkey and Saudi Arabia are among the other countries funneling money into Afghanistan.

Salehi, the target of the corruption probe, is accused of taking a bribe in return for his help in blocking an investigation of New Ansari, a money transfer business that has helped elite Afghans ship large sums of cash to overseas accounts. U.S. officials worry that the stream includes diverted foreign aid.

But authorities said the Salehi investigation is also focused on his involvement in administering the palace fund - doling out cash and vehicles to Karzai supporters - as well as his role in negotiations with the Taliban.

Salehi's job put him at the center of some of the most sensitive assignments for the Afghan government. Another national security official, Ibrahim Spinzada, has orchestrated the government's talks with the Taliban and traveled with Salehi to Dubai, Saudi Arabia and Russia.

The payments from the palace are "part of the politics here," said a second senior Afghan official. Some people receive "a special salary. It is part of intelligence activities."