THE US is very worried about corruption among Afghan leaders, top military officer Admiral Mike Mullen said overnight, warning President Hamid Karzai must crack down on offenders.

"We are extremely concerned about the level of corruption and the legitimacy of this government," Admiral Mullen said. "It's far too much endemic."

“If he doesn’t meet the conditions within six months, Obama has told him America will pull out,” said an official with access to Mr Karzai’s inner circle. “Obama said they don’t want their soldiers’ lives wasted for nothing. They want changes in Cabinet, and changes in his personal staff.”

It is extremely unlikely that British troops would stay in Afghanistan if US forces were withdrawn.

The American Embassy is understood to have warned Mr Karzai it will start collecting evidence against Wali Karzai if he is not removed from Kandahar. “They want tangible progress over the next three to six months on corruption, the culture of impunity and rising crime,” said a senior Western analyst with close links to the State Department.

“They have told Karzai they are going to start collecting evidence and if he doesn’t act on it, they will go public. We’ve never been able to back up our claims about his brother, or any of the commanders, with evidence. Now when we say something, we’ll show the smoking gun and say, ‘Arrest him’.”