(Tony Karumba/AFP/Getty Images)

The last of the 33,000 American surge troops sent to Afghanistan two years ago have left the battlefields of Afghanistan, Secretary of Defense Leon Panetta said.

With the departure of the last of the surge troops, there are now 68,000 American troops in Afghanistan.

Two years ago, President Obama announced a surge of troops to Afghanistan to help increase security amid the threat of Taliban insurgents. In announcing the deployment of 33,000 additional troops, President Obama said the surge would be temporary.

A phased withdrawal plan was developed where 10,000 troops would leave Afghanistan by July 2011 and the remaining 23,000 would leave Afghanistan by the end of September 2012.

Panetta, traveling in New Zealand on Thursday, released a statement announcing an end to the surge.

"As we reflect on this moment, it is an opportunity to recognize that the surge accomplished its objectives of reversing Taliban momentum on the battlefield, and dramatically increased the size and capability of the Afghan National Security Forces (ANSF)," Panetta's statement said. "This growth has allowed us and our ISAF Coalition partners to begin the process of transition to Afghan security lead, which will soon extend across every province and more than 75 percent of the Afghan population. At the same time, we have struck enormous blows against al Qaeda's leadership, consistent with our core goal of disrupting, dismantling and defeating al Qaeda and denying it a safe-haven."

NATO has agreed that all of its combat troops would leave Afghanistan by the end of 2014.

"It is important to underscore that even as our surge troops return home, there are roughly 68,000 Americans who remain in a tough fight in Afghanistan, alongside their NATO and Afghan partners," Panetta said. "We are a nation at war. But the international community is also strongly united behind our shared strategy to transition to Afghan security control, which will be completed by the end of 2014."

A U.S. official confirmed the withdrawal of the surge troops prior to Panetta's announcement.

The benchmark of 68,000 troops in Afghanistan reached earlier today was a development that had been anticipated for several days.

Just days ago, Pentagon figures showed there were 70,000 American troops in Afghanistan.

On Wednesday, Australian Brig. Gen. Roger Noble, the deputy operations chief for NATO in Afghanistan, refused to pinpoint for Pentagon reporters when exactly the "surge recovery" would be completed.

Noble said "not many more" surge troops remained to leave Afghanistan and that the goal of reaching 68,000 by Oct. 1 was "very, very close." He added that the timing was "very dependent on strategic lift, weather - and they change daily by sort of hundreds, if you know what I mean. "

Noble was referring to the last remaining troops that were still awaiting their flights out of Afghanistan, U.S. officials said.

There has also been a significant reduction in military equipment that matches the reduction in troops. Lt. Gen. John Terry, the commander of ISAF Joint Command, told Pentagon reporters that half of the 60,000 pieces of rolling stock and another 30,000 containers had already been shipped out of Afghanistan.

Many of the surge troops were sent to southern Afghanistan to fight the Taliban in its strongholds. As troops pushed into areas long controlled by the Taliban, the number of U.S. and NATO casualties began to rise.

Fifty-seven percent of the almost-2,000 U.S. fatalities in Afghanistan have occurred since the surge began in January 2010.

Gen. John Allen, the top NATO commander in Afghanistan, has said that in mid-November he will make a recommendation for how many more U.S. troops should leave Afghanistan in 2013.