Although the Bush administration has been trumpeting success in Iraq, the news that the United States will dispatch an additional 3,000 troops to Afghanistan highlights the difficulties it is encountering in the global war on terror. The Taliban, it is now evident, has not been defeated. It has regrouped and poses a growing threat to Afghanistan and Pakistan.

The administration had hoped to convince its NATO allies to provide the troops. After September 11, NATO invoked its famous Article 5, the pledge that an attack against one will be treated as an attack against all. Few thought to ask how a North Atlantic alliance conceived to contain Soviet expansionism could respond to a non-state threat in South Asia. Though the United States initially thanked its allies for their support, the invasion of Afghanistan was basically an American effort, assisted by local forces opposed to the Taliban.

But as the war in Iraq dragged on, Washington saw a role for NATO in Afghanistan. Initially, NATO members seemed eager to participate alongside the superpower in what they thought would be an effort at peacekeeping and reconstruction. “We would be perfectly happy to leave in three years and without firing one shot because our job is to protect the reconstruction,” British Defense Secretary John Reid said in April 2006.

To be sure, Mr. Reid also stressed that British troops would use force, if necessary, but it is doubtful he imagined the amount of force that would be required. Combat has become so intense that British troops have fired almost 4 million bullets in less than a year.

The British armed forces, like their American counterparts, are stretched. But appeals for help from NATO allies have been largely unavailing. Having sought to obtain an increase in troop commitments last fall, Secretary of Defense Robert Gates concluded that “political realities” in European members, where public opinion is souring on the conflict, meant he would have to look for other options. The result, press secretary Geoff Morrell acknowledged, is that “we will likely have to bear more of the combat shortfall” while the allies contribute in other ways.

That is a long way from the “one for all and all for one” spirit of Article 5, and it is beginning to have an impact among some members of Congress. “It is unacceptable that the United States must continue to dig deeper into its military force when some of our NATO allies are unwilling to fulfill or make robust commitments to the international effort in Afghanistan,” Rep. Duncan Hunter, the ranking Republican on the House Armed Services Committee, wrote to NATO defense ministers on Jan. 11. Mr. Hunter threatened to use the “legislative tools at my disposal” to obstruct U.S. defense contracts with countries that “have not held up their end of the bargain.”

But as the allies dither, the threat grows. The main danger now lies in our enemy’s sanctuary in Pakistan. The existence of an enemy sanctuary was decisive in the Vietnam War. After the Tet Offensive failed, North Vietnam launched its 1972 offensive. After that failed, it tried again in 1975, and this time it succeeded. We could bomb and we could interdict, but we could not deprive our enemy of its sanctuary, and we lost.

The Taliban’s sanctuary in Pakistan is an even more daunting problem, since we are hampered in using military force. We had hoped that Pakistan’s government would be able to deal with this threat, but it now appears itself to be increasingly under siege. According to the London Times, the morale of the Pakistani Army is the lowest since its defeat in the 1971 war with India. “We’re being asked to bomb our own people and shrug it off as collateral damage,” a pilot laments. “I call it killing women and children.” If Pakistan is unable to eliminate the sanctuary, it is difficult to see how NATO can succeed in Afghanistan, especially at current force levels.

As in Vietnam, our enemies will use their sanctuary as a base from which to conduct new operations. Indeed, that is how we used Pakistan after the Soviet Union invaded Afghanistan. The Soviets ultimately accepted defeat rather than take the risk of widening the war.

That future is now staring NATO in the face. If NATO fails in Afghanistan, it is questionable whether the alliance will survive. When the Cold War ended, the mantra was: “out of area or out of business.” As a result, NATO’s ambition may have exceeded its grasp, and it should focus on resolving existing problems before it assumes any additional responsibilities.