The sweep of northern Afghanistan by US-backed rebel forces has far outpaced diplomatic plans for a broad-based Kabul government, raising the possibility of anarchy and a prolonged guerrilla war against remnants of Taliban troops.
The Pentagon, while citing "definite progress" in the Afghanistan campaign, nonetheless has avoided declaring outright victory - an acknowledgment that much work remains to achieve the goal of destroying the Al Qaeda terrorist group led by Osama bin Laden.
At press time, it remained unclear whether the Taliban's wholesale retreat from the north marked the start of the regime's unraveling, or is a Taliban strategic move aimed at concentrating its weakened forces in its southern stronghold.
Key to the Taliban's survival in the south would be the support of the dominant ethnic group, the Pashtun, who represent 40 percent of Afghanistan's population and backed the Taliban's rise to power in 1996. The Taliban are predominantly Pashtun.
Yet the influential Pashtun, which has a large population in Pakistan, is also the most likely to be threatened by the Northern Alliance decision to seize the prized capital of Kabul, ignoring Washington's warnings against such a move. The Northern Alliance is composed mainly of Tajik, Hazara, and Uzbek ethnic minorities.
The Northern Alliance victories could push the Pashtun to rally behind the Taliban - or at least not abandon them - until they are assured strong political representation in Kabul. "[The Pashtun] will not go against the Taliban until there is a credible alternative," says former Afghan colonel Ali Jalali.
The United States, Britain, Pakistan, and other allies in the Afghanistan campaign pressed ahead with UN-sponsored plans to form an ethnically broad-based coalition government in the country, with calls for an international peacekeeping force to enter Kabul to maintain stability.
Indeed, experts say the full leverage of the international community, combined with a robust peacekeeping force, is essential to bring a modicum of political stability to Afghanistan, a nation ravaged by decades of foreign occupation and religious and ethnic conflicts.
"It's a multiethnic society, and they all want to live within those borders, but they are remarkably zero-sum-game in the way they conduct their politics," says Charles Dunbar, a foreign-policy expert at Simmons College in Boston and former US diplomat in Afghanistan. "That is why you need an outside force helping them in a muscular way to sort out their political future."
The Bush administration expressed both pleasure over Northern Alliance gains and concern over its entry into Kabul. Amid scattered reports of executions and revenge killings, Washington urged the opposition to demonstrate "tolerance" and avoid settling old scores. Washington seeks to prevent a repeat of the atrocities that took place under Northern Alliance rule from 1992 to 1996, when tens of thousands of people died during infighting by rival factions on the streets of Kabul.
Experts warn of the risk that - before the slow-moving UN nation-building process can succeed - Afghanistan may revert in the north and south to the fragmentary, pre-Taliban rule of regional strongmen, each controlling a distinct turf. Indeed, one Northern Alliance official in Washington strongly hinted at that possibility.
"Perhaps a decentralized regime in Afghanistan would be the easiest way to solve the problem," the official said. "We should make use of different strong personalities, who can establish strong administrations in different zones."
Such a politically fractured Afghanistan would increase the prospect for internal chaos, allowing the Taliban and terrorist groups to survive more easily, analysts say.
Indeed, the dramatic power shift in Afghanistan in recent days illustrates how the US-led coalition's military push to eliminate the Taliban and Al Qaeda also depends on progress toward the long-range diplomatic goal of a broad-based Kabul regime.
Washington needs to ensure Pashtun leaders a political role to win their help in routing the Taliban and, in turn, prevent a drawn-out guerrilla war.
The Pentagon has for weeks voiced frustration and impatience over the hesitation of Pashtun leaders to rise up against the Taliban. That reluctance has left US military commanders without a proxy force in the south, contributing to this week's lopsided military successes.