WASHINGTON -- A senior defense official in Afghanistan says the war's top commander, General David Petraeus, has told the White House that although President Obama's troop surge has made progress in some of the more violent regions of the country, much more work needs to be done to defeat the Taliban.

The White House is expected to release a much anticipated review of the Afghan war strategy sometime next week.

According to this official, who spoke to reporters in Afghanistan on the condition of anonymity, one of the bigger recommendations that General Petraeus will provide has to do with future size of the Afghan National Security forces. Last month NATO leadership agreed to a plan to hand over security operations to Afghan forces by the end of 2014.

Pentagon Press Secretary Geoff Morrell, who was in the room when this official briefed, cautioned reporters that the review is not yet complete and therefore nothing is final. "We are still in the midst of this review, there is no final product so it's premature to draw any definitive conclusions," Morrell said.

Defense Secretary Robert Gates, who is travelling in the region, met with commanders operating along the Pakistan border, in the violent southern provinces of Afghanistan. "These guys, being close to the border, do face some special challenges and have taken some serious losses," Gates said. "But... I've heard a lot of confidence in the feeling that there may be more headway."

Earlier Tuesday, Gates met with members of the platoon that was attacked by a rogue Afghan border police officer last week. He called that visit "inspiring."

Gen. Petraeus told ABC News in an interview that aired Monday he was not entirely confident the Afghans could take over security by 2014. "I think no commander ever is going to come out and say, 'I'm confident that we can do this,'" Petraeus told ABC. I think that you say that you assess that this is-- you believe this is, you know, a reasonable prospect and knowing how important it is-- that we have to do everything we can to increase the chances of that prospect."

Military leadership in Afghanistan has acknowledged that the training mission for Afghan police has been one of the biggest challenges.

"But again, I don't think there are any sure things in this kind of endeavor. And I wouldn't be honest with you and with the viewers if I didn't convey that," Petraeus said.