The commander of the International Security Assistance Force in Afghanistan is warning his top commanders of new risks of attacks due to rising tensions between NATO forces and the Afghan president, an ISAF official told CNN Thursday.

The personal email Gen. Joseph Dunford sent Wednesday is not a formal threat advisory, said the official, who did not want to be identified.

The tensions between the NATO-led coalition forces -- especially those from the United States -- and President Hamid Karzai escalated after a bomb blast in Kabul last weekend that killed nine people.

Karzai said afterward that there are "ongoing daily talks between Taliban, American and foreigners in Europe and in the Gulf states."

Dunford quickly denounced Karzai's remark.

"We have fought too hard over the past 12 years. We have shed too much blood over the past 12 years. We have done too much to help the Afghan Security Forces grow over the last 12 years to ever think that violence or instability would be to our advantage," he said.

In the email sent Wednesday, Dunford told commanders that Karzai's recent statements "could be a catalyst for some to lash out against our forces -- he may also issue orders that put our forces at risk."

ISAF is currently in discussions with the Afghan government about the terms for the turnover of the detention facility at Bagram to the Afghans, as well as the withdrawal of U.S. special forces from Wardak Province following still unsubstantiated complaints about U.S. troop misconduct there.

Dunford met with Karzai Wednesday to discuss the transfer of the detention center. The general said it "must be done in a way that meets the needs of Afghan sovereignty while mitigating the real threats that some of these detainees pose to Afghan and coalition forces.

"We will complete the transfer when the remaining issues have been resolved," Dunford said in a statement on ISAF's website.

Several media reported Karzai gave a speech Tuesday in which he suggested the government would take unilateral actions to assume control of the detention center if the transfer was delayed much longer.

In his email, Dunford calls Karzai's remarks about Bagram "inflammatory speech."

ISAF called the general's warning "prudent given increased coalition casualties in recent days."

"ISAF routinely conducts assessments and adapts its protection posture to ensure our forces are prepared to meet potential threats and that they have a common understanding of the situation here in Afghanistan," the ISAF statement said. "General Dunford's email is simply an example of this vigilance."