The new head of US forces in Afghanistan is reserving the right to back away from the July, 2011, deadline set by the Obama administration to begin withdrawal of US forces.

Gen. David Petraeus, who took over as commander of the Afghanistan war effort from Gen. Stanley McChrystal last month, told NBC's Meet the Press that the nature of the withdrawal will depend completely on conditions on the ground at the time.

"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 told NBC's David Gregory in an interview taped in Kabul.

"So you'll take a hard look at this and you'll make a determination about when America's footprint should be diminished?" Gregory asked.

"Absolutely," the general responded.

Petraeus cited Vice President Joe Biden, who said several weeks ago that the initial phase of the "withdrawal" may only involve "a couple of thousand" troops.

Petraeus' comments come as opinion polls show diminishing support for the Afghanistan war effort. And while Petraeus asserted that the US military is achieving "areas of progress," the news from Afghanistan suggests the war there is deadlier than ever. July was the deadliest month for US troops in Afghanistan, with 66 American lives lost.

Petraeus also condemned the "reprehensible" release of Afghan war documents on Wikileaks.

"As we have looked through it more and more, there are source names and in some cases there are actual names of individuals with whom we have partnered in difficult missions in difficult places.

"And obviously, that is very reprehensible."

He said the release of the documents, though consisting of raw documents that were not top secret, was "beyond unfortunate."

"I mean, this is a betrayal of trust," he said.

His comments came in response to a threat by the founder of the whistleblowers' website WikiLeaks, Julian Assange, to make public another batch of secret documents in a "couple of weeks" despite mounting Pentagon protests.

WikiLeaks has already released 76,000 military documents from the Afghan conflict, but is still holding another 15,000 classified files.

On Meet the Press, Petraeus said he was not sure what might be in them.

-- With a report from AFP

This video is from NBC's Meet the Press, broadcast Aug. 15, 2010.

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