The US commander in Afghanistan said he sees "areas of progress" in the war but it was still unclear if President Barack Obama's goal of starting to pull out troops in July 2011 could be met.

Army General David Petraeus said in an interview aired on Sunday on NBC's "Meet the Press" that the battle against the Taliban insurgency was an "up and down process" and it was too early to determine its success.

"What we have are areas of progress. We've got to link those together, extend them," Petraeus said in an interview aimed at boosting flagging public confidence in the war effort.

He said he would give his "best professional military advice" to Obama about the July 2011 target for starting withdrawals and leave the politics of the war to the president, who will be up for re-election in 2012.

"I think the president has been quite clear in explaining that it's a process, not an event, and that it's conditions based," Petraeus, who replaced General Stanley McChrystal as Afghan commander less than two months ago, said of the target date for starting withdrawals.

"It would be premature to have any kind of assessment at this juncture about what we may or may not be able to transition," Petraeus said.

Obama, who announced in December he was adding 30,000 more US troops in Afghanistan, plans a strategy review in December after the elections. While Congress supported his plan to bolster troop levels, polls show the public remains dubious about the effort.