As he prepared to leave for Europe for two meetings with key allies to discuss the way forward in Afghanistan, U.S. Defense Secretary Robert Gates said President Barack Obama's new strategy has about a year to at least begin to show progress.

Secretary Gates flies overnight to meet with his NATO counterparts and with officials from nations with troops in southern Afghanistan, the strongest area for the Taliban and allied groups. The meetings come as the first of 21,000 additional U.S. Marines have begun patrolling in the southern region, as part of President Obama's new strategy.

Gates told a U.S. Senate committee that this is a particularly important period in the long Afghanistan fight as the president's new strategy is being implemented, more U.S. troops are arriving and new American commanders are preparing to take up their posts. He said the Obama plan has about a year, maybe 18 months, to demonstrate that it can work, or it will lose the support of the American people. But Gates said the effort will need to last substantially longer than that.

"This problem will not be over in 18 months. This problem will not be over in two years. This is, let's be honest, a long-term commitment that we are involved in in Afghanistan, if we are to ultimately be successful," he said.

Gates also reported that the administration has finished developing long-overdue benchmarks to measure its progress in Afghanistan in the coming months. But he did not say what they are. The president's strategy calls for increased efforts to protect Afghan civilians, improve the country's economy, and build the competence and credibility of the Afghan government alongside military efforts to defeat insurgent and terrorist groups.

Gates said he has been encouraged by Pakistan's recent strong offensive against militants on its side of the border. "The newest development of the Pakistani Army taking on these extremists in [the] Swat [Valley]and elsewhere, I think is an extremely important development. And the possibility of the Afghans, the Pakistanis, ourselves and our allies together working against this problem has given me more optimism about the future than I've had in a long time in Afghanistan," he said.

And as he prepared to meet with allies, Gates had some complementary words for their efforts, which U.S. officials have frequently criticized as undermanned, under-funded and overly restrictive.

"We have forty-some other nations there as our allies. This is not just the United States carrying this by ourselves. Now, do we wish they had more troops? Do we wish they spent more money? Absolutely. But the fact is, our allies have 32,000 troops in Afghanistan. This is not a trivial commitment on their part," he said.

Gates noted particularly the contributions of Canada, Denmark, Britain and Australia for being "in the fight" and taking a large number of casualties.

Although many European nations have refused to send more combat troops to Afghanistan, some European countries are concerned about what they see as a virtual U.S. takeover of the mission. The increased U.S. commitment will bring America's troop total to 68,000 -- slightly more than double the combined total of other allies. The United States is also adding a three-star general as deputy commander of U.S. forces, but NATO has not agreed to allow that officer to command its forces.