Eighteen months into the Obama Administration, the American focus has shifted sharply from Iraq to Afghanistan. The U.S. once again has more troops in Afghanistan than in Iraq. And Fiscal Year 2010 marks the first time the U.S. will spend more money there as well.

U.S. and NATO Commander in Afghanistan General Stanley McChrystal is implementing a new counterinsurgency strategy that emphasizes protection of the population, establishing good governance and uprooting the Taliban from their traditional strongholds.

McChrystal's strategy is sound. But it will require time - and adequate resources - to succeed. That's not an easy sell for an American public strapped by the worst economy since the Great Depression and weary from eight years of war in two countries.

But there is no good alternative to McChrystal's approach. A victorious Taliban emboldened by a U.S. retreat would be more inclined than ever to support al-Qaida and its terrorist affiliates who remain intent on attacking our homeland.

Moreover, a strengthened Taliban in Afghanistan would buoy extremists and fuel unrest in nuclear-armed Pakistan. In this scenario, U.S. national security would be in far more danger than it was before 9/11.

President Obama should be commended for his December decision to send another 30,000 U.S. troops to Afghanistan. It will raise American troop levels there to nearly 100,000 by year's end. Yet the President has also sent mixed signals about a long-term commitment to the war, and that severely undermines U.S. ability to achieve success in Afghanistan.

By highlighting that the U.S. will begin withdrawing troops in July 2011, President Obama signals to Afghans and others that the U.S. is not truly committed to prevailing over the Taliban.

This weakens Afghan resolve to resist the Taliban now for fear they will be back in power in the near future. It also reinforces Pakistan's inclination to hedge on its support for the Afghan Taliban leadership based on its territory.

These mixed signals are found in the National Security Strategy released by the Obama Administration last week.

The document highlights the need to succeed in Afghanistan and to prevent the Taliban from overthrowing the Afghan government. But this resolute language is coupled with a reiteration of the President's promise to reduce troop levels beginning in mid-2011.

President Obama must understand that premature withdrawal of U.S. troops fuels the perception in the region that Taliban victory is inevitable. That can only undermine his own strategy.

U.S. military commanders are now racing against time to demonstrate they can reverse Taliban battlefield momentum by December, the due date for the next major Afghanistan policy review. This is challenging, but possible.

Earlier this year, U.S. and coalition forces, along with their Afghan counterparts, ousted the Taliban from one of their strongholds in Marjah in southern Helmand Province. But insurgents still lurk in the town, intimidating citizens who cooperate with the Afghan government and coalition forces. The coalition must figure out how to strengthen communities to resist the Taliban and to ensure the local police have the trust of the people.

U.S. forces are pouring into the Taliban's birthplace and center of gravity, Kandahar. They're preparing for an operation that U.S.

Chairman of the Joint Chiefs of Staff Admiral Mullen calls "the cornerstone of our surge effort." Uprooting the Taliban from Kandahar would demonstrate the coalition's determination to prevent Taliban domination. It also would boost Kabul's efforts to reconcile non-ideological Taliban fighters with the government.

The success of the Kandahar initiative will hinge on the coalition's ability to quickly deliver security, development assistance and good governance to the people. If the U.S. focuses on these objectives, there is a good chance this summer's push will spell the beginning of the end for the Taliban.

Lisa Curtis is a senior research fellow at The Heritage Foundation