U.S. Secretary of Defense Robert Gates said Tuesday that he expects President Barack Obama to make decision on sending additional deployment to Afghanistan within "next few days."

He told reporters at a Pentagon press conference that such a decision must be made before the completion of an ongoing overall policy review on Afghanistan.

That is because the troops will need to take some time to prepare for their new deployment, said Gates.

Earlier in the day, Obama assigned former CIA officer Bruce Riedel to lead an interagency policy panel to lead a policy review on Afghanistan and Pakistan, which will be completed before the NATO summit in April.

Without going into the details, Gates said he has presented several options for Obama on the military buildup.

He also said the additional deployment for Afghanistan is made possible because of a gradual drawdown of U.S. troops in Iraq.

It's still unclear how many additional troops will be deployed in Afghanistan under Obama's upcoming decision, but military officials have said the number won't go beyond 30,000.

There are about 36,000 U.S. troops in Afghanistan at the present.