Hopes for a potentially decisive ground victory against Afghanistan's ruling Taliban government suffered an apparent setback Wednesday as Taliban forces held off rebels in the battle for the strategically important city of Mazar-e Sharif.

The Northern Alliance launched its attack early in the day, confident it could take the city within days and bolstered by the Pentagon's assertion that the Taliban is less able to respond to the barrage from U.S. warplanes, now concentrating on the capital, Kabul, and Kandahar, the Taliban's home base.

As President Bush left the U.S. for a meeting in China, he warned that the struggle against terrorism likely will last beyond the campaign against Osama bin Laden, the prime suspect in the Sept. 11 suicide hijacking attacks, and the Taliban regime sheltering him.

"People are going to get tired of the war on terrorism," Bush said at Travis Air Force Base in California. "And by the way, it may take more than two years."

Secretary of State Colin Powell sought to maintain the delicate coalition against terrorism, assuring India officials that the U.S.' critical alliance with Pakistan will not come at India's expense. Tensions between Pakistan and India flared this week with the two nuclear powers exchanging artillery fire in the disputed Kashmir region.

Later in Shanghai, Powell said the deteriorating situation in Afghanistan might lead to a political vacuum, requiring United Nations peacekeepers to stabilize the country.

"This isn't the United States going in and nation-building with troops," Powell said. "This is helping the international community, helping the people of Afghanistan to create hopeful conditions within the country."

In Washington, Pentagon officials said special operations troops were ready for search-and-destroy missions against terrorists and their supporters in Afghanistan.

Military officials said helicopter-borne special forces were put aboard the carrier USS Kitty Hawk in the Indian Ocean several days ago, but the officials would not discuss their possible deployment. The Pentagon has not acknowledged the presence of any ground forces in Afghanistan but has said ground forces will be needed to uproot bin Laden and his Al Qaeda network.

Bush said the U.S.-led air assaults were "paving the way for friendly troops on the ground" to rout the terrorists. But aides said the president was referring to anti-Taliban forces in northern Afghanistan, not American or British troops.

One indication of the situation in Afghanistan came from reports that Taliban soldiers had seized the two main UN food storehouses near Kabul, taking more than half of the food relief set aside to feed an estimated 2 million Afghans during the coming winter.

In the key city of Kandahar, residents said by telephone that Taliban fighters were handing out weapons to civilians.

About 150 men armed with rocket-propelled grenades and assault rifles were guarding the Kandahar compound of the Taliban's supreme leader, Mullah Mohammed Omar. The compound has been struck repeatedly during the campaign.

Omar called on Afghans to rally in what he described as a holy war. "It is jihad against the infidel like the one we waged against the Soviets," the Pakistan-based AIP news service quoted him as saying Wednesday. "I am confident that, with the grace of Allah, we will force to his knees and defeat the great infidel."

Battle for Mazar-e Sharif

In Mazar-e Sharif, scene of frenetic street fighting and large-scale massacres three years ago when the Taliban wrested the city from the Northern Alliance, hopes for a quick rebel victory dimmed.

A rebel victory could allow the United States and its partners in the anti-terrorism coalition to use the city's airport as a launch pad for air strikes and other operations against the Afghan capital and other Taliban fortifications.

Navy Rear Adm. John Stufflebeem, deputy director of operations for the Joint Chiefs of Staff, described the fighting at Mazar-e Sharif as "back and forth."

That assessment from the Pentagon raised fears that fierce street battles are ahead as Taliban fighters dig in, and deepened concerns that Northern Alliance leaders may be too optimistic about their abilities.