Sept. 29, 2009 -- The stage is set for what could potentially be one of most difficult decisions President Obama will make as commander-in-chief: whether or not to send more U.S. troops to Afghanistan.
Members of the National Security Council met Tuesday for the first of four meetings scheduled in the coming weeks to reassess the path forward in Afghanistan.
Obama, who did not attend today's session, told reporters after a meeting with NATO Secretary General Andres Rasmussem that the mission in Afghanistan was "dismantling, disrupting, [and] destroying the al Qaeda network" and the U.S. is "effectively working with the Afghan government to provide the security necessary for that country.
Whether completing that mission will necessitate more U.S. troops is now the central question receiving substantial debate - and there are no indications Obama will make a decision quickly.
Defense Secretary Robert Gates -- who received General Stanley McChrystal's much-anticipated request for more U.S. forces late last week -- has said he will keep the report secret "until such time as the President and his security team are ready to consider it," according to Pentagon spokesman Geoff Morrell.
Obama and his advisors have signaled publicly that they may seek to redefine the mission in Afghanistan and Pakistan.
Experts say as many as 10,000 to 40,000 more troops could be required for the mission in Afghanistan, where 68,000 U.S. soldiers are already expected by year's end.
"My sense is that 20,000, 25,000 American troops is enough to start turning the tide over the course of 2010 and is probably a price the American army can bear and that Afghanistan can support," said retired Army Lt. Col. Dr. John Nagl, President of the Center for New American Security, in an interview with ABC News.
Nagl says the additional troops would help dramatically increase recruitment and training of Afghan national army and police forces and provide the ability to secure and hold Kandahar, which is the de facto capital of opposition Taliban forces.
Support Within Congress and the Administration for a Troop Surge Has Appeared Increasingly Thin
"We've had an under-resourced counterinsurgency strategy for essentially our entire time there, and we're going to have to provide additional resources to turn the Taliban's momentum around," Nagl said.
"Failing to do so, in my eyes, gives the Taliban additional strength and makes it more likely that they're going to be able to put more pressure on the government of Afghanistan and on the government of Pakistan."
Support within Congress and the administration for such a troop surge has appeared increasingly thin, as public support for the war in Afghanistan also continues to wane, according to most polls.
Former National Security Advisor Zbigniew Brzezinski told ABC News that more U.S. troops in Afghanistan may only embolden the Taliban, who already paint U.S. and NATO forces as "occupiers."
"I think [more troops] will intensify the opposition to us. It's as simple as that. I think we will be viewed increasingly by a larger and larger number of Afghans not as allies in a shared cause but as alien occupiers," Brzezinski said.
"I'd like to see if we can increase the level of political involvement in local accommodations in responding to the decentralized reality in Afghanistan, and I'd like to see more of an international effort not only involving Pakistan but also China."
Efforts to diversify and enhance international support for the mission in Afghanistan have been ongoing for years but have had mixed results.
"I'm not sure how energetically we have tried to do that," Brzezinski said. "I'm not sure how energetically we have discussed what possible outcomes there are in Afghanistan that might be of special interest to the Pakistanis who could be more helpful in terms of cross border insurgency. It is essentially a question of emphasis rather than a dramatic turn in our strategy."
Still, critics say enough has changed in Washington and Afghanistan since the last strategy review -- including an ongoing dispute over the credibility of the recent Afghan national elections -- that a more fundamental shift in the war's direction is necessary.
McCain: Stakes are Too High for Obama to Abandon the Counterinsurgency Strategy
But former presidential candidate Sen. John McCain, R-Ariz., a supporter of the troop surge in Iraq, tells ABC News the stakes are too high for the President to now abandon the counterinsurgency strategy he unveiled in March.
"We have the strategy, now we need to implement the strategy," McCain said.
"I have some sympathy for the president because I understand that a part of the base of his party is adamantly opposed," said McCain. But "the longer we delay in implementing that strategy, which means additional troops, the more danger the 68,000 that are already there are in."
In March, Obama endorsed "executing and resourcing an integrated civilian-military counterinsurgency strategy" in Afghanistan. He later replaced the commander of U.S. forces in Afghanistan, General David McKiernan, with McChrystal, widely regarded as a counterinsurgency expert.
President Obama has indicated he may now be reconsidering that approach. He told ABC's George Stephanopoulos during an interview on "This Week" that he will not consider sending additional troops to Afghanistan until a thorough review of General McChrystal's security assessment is complete.
That document - separate from the forthcoming troop request - was leaked to the Washington Post last week.
"I just want to make sure that everybody understands that you don't make decisions about resources before you have the strategy ready," Obama said.
Just what the strategy will be going forward -- and whether more troops will be required -- depends in large part on how the Administration chooses to define "success."
"A pretty base level requirement" for that definition, says Nagl is "an Afghanistan with sufficient security forces and a good enough government to get enough support from its people that they prefer the government to the Taliban."
"These are long hard wars," added Nagl. "You're not going to see drastic immediate progress."
ABC News' Luis Martinez and Richard Coolidge contributed to this report.