After a grueling day of testimony on Capitol Hill, Defense Secretary Robert Gates told ABC News' Charlie Gibson today in an interview for "World News" that President Obama's target of July 2011 for U.S. troops to begin withdrawal from Afghanistan is not absolute.
The president "said it would be a responsible drawdown based on conditions on the ground. July 2011 is the beginning of a process," Gates said.
Gates said any drawdown in U.S. troops after that date – ceding responsibility for security to Afghan forces – would rely on a favorable progress report in December 2010 and be a "very gradual process" if it moves forward.
Watch Defense Secretary Robert Gates' interview with Charles Gibson tonight on World News at 6:30 p.m. ET.
"What we've tried to do… is balance," Gates said, "signaling strong resolve to our own troops, to the Afghans, to the Pakistanis and to the Taliban that we are in this to be successful."
Gates told Gibson the target date is also intended to pressure the Afghan government to do more, quickly, to provide for its own security. "We want to light a fire under them," Gates said.
The defense secretary also suggested the coupling of a surge in troops with a target date for the beginning of their withdrawal would also placate a war-weary American public.
"We have to send some signal to them as well that this is not an open-ended commitment," he said.
Earlier Wednesday, Gates testified before both the Senate Armed Services and House Foreign Affairs Committees to explain Obama's new strategy for Afghanistan that involves sending 30,000 more troops to the region and a target date of July 2011 to begin their withdrawal. He was joined on the Hill by Secretary of State Hillary Clinton and Chairman of the Joint Chiefs of Staff Adm. Mike Mullen.
Gates said he signed the orders for the troop deployment last night on Air Force One following the president's speech at West Point. The first troops that are part of the surge will begin arriving in Afghanistan in two weeks, he said.
"The vast preponderance will be there by the end of July… all will be in by the end of August, early September," Gates said.
Gates reiterated the administration's confidence in the plan, saying the president's military and civilian advisors are united in the face of critics.
One of those critics, Sen. John McCain, R-Ariz., said on "Good Morning America" Wednesday that setting a target date for beginning a drawdown in U.S. troops in Afghanistan may "embolden the enemy" who will "wait us out."
"What does 'wait us out' mean?" Gates responded to Gibson. "The Taliban has been as aggressive today as we've ever seen them be…and if they lie low, that'd give us huge opportunity…. We're sending 100,000 American troops in there to take these guys on… our purpose is to degrade their capability enough that the Afghan national security forces can then take responsibility for security in those areas."
Read the latest on the war in our special section, Fight for Afghanistan.