Updated at 6:58 p.m. EST
The top U.S. commander in Afghanistan told lawmakers that President Obama's new war strategy is achievable and that combat force levels can be reduced starting in the summer of 2011, while acknowledging that the goal of stabilizing the war-torn region will be "undeniably difficult."
Gen. Stanley McChrystal, appearing before House and Senate panels a week after Mr. Obama, said he supports the plan without reservation. He would have preferred more forces that he is being given, and he said he had not recommended the 18-month expiration date for the surge that Mr. Obama applied.
"I'm comfortable with the entire plan, sir," McChrystal told a skeptical Sen. Carl Levin, a Democrat and chairman of the Senate Armed Services Committee.
McChrystal said strategy was a "realistic and effective approach" that "recognizes that the next 18 months will likely be decisive, and ultimately, enables success."
"We can and will accomplish this mission," McChrystal said.
The general gave Congress milestones to judge whether the surge is working, reports CBS News National Security Correspondent David Martin.
McChrystal gave senators three dates, starting with July 2010.
"I expect there to be significant progress that is evident to us inside our force," McChrystal said.
Next, December 2010.
"I expect that we will be able to lay real progress out that will be clear to everyone," McChrystal said.
Finally, July 2011.
"I think the progress will be unequivocally clear to the Afghan people," McChrystal said. "When it's unequivocally clear to them, that will be a critical decisive point."
McChrystal also said capturing Osama bin Laden is the ultimate key to defeating the al Qaeda terror network, though he distinguished that goal from stabilizing Afghanistan.
McChrystal told Congress on Tuesday that bin Laden is an "iconic figure" whose very survival eight years after the Sept. 11, 2001 terrorist attacks on the U.S. serves as a recruiting tool for al Qaeda. U.S. intelligence officials believe bin Laden is in hiding in Pakistan, along that country's rugged border with Afghanistan.
McChrystal said finding bin Laden is not the key to winning the war in Afghanistan. But he said he does not think that the United States will defeat the terror network outright until bin Laden is found and brought to justice.
Ambassador Karl Eikenberry, who had voiced misgivings previously, also endorsed the president's new approach at the Capitol Hill hearing.
The two men sat side by side at a pair of congressional hearings long sought by Republicans critical of the lengthy White House review that yielded the decision to send an emergency infusion of 30,000 additional U.S. forces. Although they took pains to say they are friends, they displayed none of the hand-in-glove unity of the Gen. David Petraeus and U.S. ambassador Ryan Crocker, who mananged the Iraq surge nearly three years ago.
Sen. John McCain, the senior Republican on the panel, pointedly told the men he hopes that any differences they have are put to rest. He praised the decision to send additional U.S. forces but said the deadline to begin bringing them home is a mistake.
"We have announced a date divorced from conditions on the ground," McCain said.
The new battle strategy includes a plan to begin bringing some troops home in 18 months - a number to be determined by conditions on the ground at that time.
"Results may come more quickly," McChrystal told lawmakers. "But the sober fact is that there are no silver bullets. Ultimate success will be the cumulative effect of sustained pressure."
Eikenberry said the course outlined last week by Mr. Obama "offers the best path to stabilize Afghanistan and to ensure al Qaeda and other terrorist groups cannot regain a foothold to plan new attacks against our country or our allies."
Rep. Ike Skelton, D-Mo., the committee's chairman, said Mr. Obama did the right thing by ordering an additional 30,000 U.S. troops. But he opened the hearing by ticking off a series of questions, asking what success will look like, how it will be measured, "what risk are we accepting in the next 18 months and how can we mitigate it?"
McChrystal assured Skelton that the troop infusion will work. "I believe we will absolutely be successful," the general said.
The House panel's highest-ranking Republican, Rep. Howard "Buck" McKeon of California, told McChrystal he was waiting to hear how "the president is not under-resourcing his own strategy," since the general has sketched ways that as many as 80,000 additional U.S. forces could have helped turn the tide.
Under questioning later from McKeon, McChrystal said he did not think he would need to ask for any more troops in a year's time, but would not hesitate to recommend more if circumstances change.
He also told McKeon he did not recommend the July 2011 exit plan, but that he supports it. He said he made no recommendations at all about the exit plan.
"By the summer of 2011, it will be clear to the Afghan people that the insurgency will not win, giving them the chance to side with their government," McChrystal said. "From that point forward, while we begin to reduce U.S. combat force levels, we will remain partnered with the Afghan security forces in a supporting role to consolidate and solidify their gains."
Eikenberry sought to clarify his stance during the three-month review, widely-reported as aat a time when there were still so many questions surrounding the corruption and mismanagement that have stained the Karzai administration.
"It was not a question of additional troops," he said Tuesday. "It was a question of the number of troops ... the timelines... the context that those troops would operate in."
Asked what his biggest challenges will be, McChrystal said growing the Afghan security forces in size and quality, bolstering the quality of Afghan government and convincing the Afghan people to support their government even as they are being "coerced by the Taliban."
McChrystal said in his opening statement that one of the reasons he believes he can accomplish his mission is that Afghans accept the U.S. role there.
"Afghans do not regard us as occupiers," he said. "They do not wish for us to remain forever, yet they see our support as a necessary bridge to future security and stability."
He said the nature of the Taliban and the way it ruled before being overthrown in late 2001 are among reasons he thinks this insurgency can be defeated, when others in history have often been immune to outside military efforts.
"They were not credible in power and they are not credible now," McChrystal said. "They are not the National Liberation Front of Afghanistan."
McChrystal predicted improvement in Afghan security forces, who eventually must take responsibility for protecting their own country.
"My expectation is the insurgency will be less robust in the summer of 2011, significantly so, and my expectation is that the Afghan national security forces will be more robust," McChrystal said, although "still imperfect." Defense Secretary Robert Gates last week said that the idea is to degrade the Taliban "to levels manageable" by the Afghan forces.
, Gates reiterated that the administration expects the withdrawal, beginning in July 2011, to be "a several-year process - whether it's three years or two years or four years remains to be seen."
Afghanistan President Hamid Karzai said his country willto build homegrown security forces well beyond that date. "For a number of years, maybe for another 15 to 20 years, Afghanistan will not be able to sustain a force of that nature and capability with its own resources," Karzai said during a joint news conference with Gates in Kabul.
McChrystal's congressional appearance followed a particularly pointed assessment of the stakes in Afghanistan from his boss, Joint Chiefs of Staff Chairman Adm. Mike Mullen, on Monday.
"We are not winning, which means we are losing," Mullen told troops who will soon go to Afghanistan as part of the first wave of the surge. As the U.S. and its partners lose ground, insurgents gain new recruits, Mullen said. "That's why we need the 30,000" and the fast deployment calendar that Mr. Obama chose, Mullen told troops at Camp Lejeune in North Carolina.