A U.S. soldier on patrol in Khost province in February 2009.

Barbara Starr
CNN Pentagon Correspondent

The Pentagon is considering a significant overhaul in how it deploys critical military units to Afghanistan to fight the insurgency, a U.S. military source tells CNN. The change is based on the experience in Iraq of special operations units commanded by Lt. General Stanley McChrystal. McChrystal is slated to become the next top commander in Afghanistan if he is confirmed by the Senate.

The plan is evolving as Defense Secretary Robert Gates is expressing growing concern that American public support for the war in Afghanistan will begin declining unless the Obama Administration can demonstrate progress in improving the security situation by the end of this year according to his top spokesman.

Pentagon press secretary Geoff Morrell tells CNN that Gates believes “its critically important” for both the US and Afghan governments to make progress in the coming months although “that doesn’t mean you have to have decisive gains,” Morrell said.

Secretary Gates believes the Taliban has momentum in southern Afghanistan at this time, Morrell said. But with more than 20,000 additional US troops on the way to the warzone, people want to see “tangible” progress, Morrell said.

Gates’ concerns about potential declining US public support for the war were recently underscored in an interview with the Wall Street Journal.

“People are willing to stay in the fight I believe, if they think we’re making headway. If they think we’re stalemated and having our young men and women get killed, then patience is going to run out pretty fast,” he told the newspaper in an interview.

The new idea being considered calls for hundreds, perhaps thousands, of troops to train and deploy as a unique battlefield organization, specializing in counterinsurgency warfare. The official emphasized the troops could engage in a full spectrum of operations ranging from combat, to providing medical care. In Iraq, the strategy was used to great effect on a smaller scale within the Joint Special Command, which McChrystal commanded.

“We want cohesive units, fleet of foot, specializing in counterinsurgency warfare,” the official said. The troops would deploy separately from routine deployments by other support units. But given that thousands of additional combat forces are scheduled to arrive in Afghanistan in the coming month its not clear how this new plan would be implemented within the structure of the expanding conventional force.

After serving in the war zone, the new units would come back but still stay together and most importantly stay informed on the area of Afghanistan in which they served though intelligence and military assessments. Then, when its time to return to the war zone, they would go back to the same area. The goal is develop troops with growing expertise in a particular region, the official said. And the additional benefit is the unit would build up a level of confidence with local and provincial Afghan officials who would come to know them over time.

The official underscored that one complaint the US military continues to hear from the Afghans is that US troops come to a region, serve a year and then the Afghan ‘never see them again.” This puts the incoming troops at a continuing disadvantage in a culture which values ongoing personal interaction.

The official said this type of organization closely mirrors how McChrystal operated in Iraq when he led the Joint Special Operations Command, the official said. However the idea is likely to be difficult to initially implement and it could be controversial inside the military. One potential idea calls for troops to deploy more often but for shorter tours of duty than the current 12 months. That could put further strain on military families. In addition, if troops have career expertise only in one area, it could hurt their chances for advancement within the military.

The official also noted that under McChrystal the US military will be “stepping up its intelligence game” in Afghanistan, gathering more intelligence on specific insurgent leaders, and conducting more reconnaissance and surveillance.

The plan is preliminary, and has not yet been approved by Admiral Michael Mullen, chairman of the Joint Chiefs of Staff or Defense Secretary Robert Gates, the source said. But Mullen several weeks ago asked McChrystal to develop a plan to provide innovative ways to increase the US military focus on Afghanistan which is now the top military priority, a senior military official tells CNN. The official briefed CNN on the plan, but declined to be named because it is all still in the preliminary stages, and many decisions have yet to be made.

Mullen now believes the U.S. military must fundamentally improve the security situation in Afghanistan in the next 12 to 24 months, the official said. That is the fundamental reason the chairman decided to press for McChrystal to become the top commander, based on his counterinsurgency field experience in Afghanistan.