The Sept. 11 attacks generated unprecedented global consensus for war against the perpetrators. And there is at least as much consensus on a second point: that the 189-member UN take a leading - if not the leading - role in the war.
The UN has already given the US-led campaign in Afghanistan a crucial stamp of approval. It is also on the front lines, dealing with the humanitarian consequences. And though UN officials are loath to use the term "nation-building," they enthusiastically cite their institution as the best-equipped to help rebuild the Afghan state.
Still, memories are fresh of recent UN missions that foundered as political will and resources dwindled. "Sept. 11 shocked the world into an extraordinary degree of consensus," says a top UN official. "The question is, can it be sustained?"
Over the past decade or so, the UN has been called on to clean up the residue of cold war-era conflicts, or those spawned after the war's end. From Angola, to Bosnia and East Timor, this world body has taken on jobs no one else wanted - and has suffered its share of humiliations.
"We have to show the world that this time it's not business as usual, and the UN can really make a difference in this global fight against terrorism," says Andre Erdos, the Hungarian ambassador to the UN and chairman of the UN disarmament and international security committee.
For the UN, Afghanistan is actually a rematch. In 1999, political infighting among the assorted Afghan factions, and neighbors Pakistan and Iran, harpooned UN efforts to broker peace in a country devastated by two decades of civil war. The UN special envoy from that effort, veteran Algerian diplomat Lakhdar Brahimi, has been reappointed to the post.
Mr. Brahimi says the renewed enthusiasm for resolution is palpable. But there is not yet a concrete plan, only agreement that the government to replace the Taliban must be broad-based and stable. Brahimi is headed to Rome later this week to meet with former Afghan king Zahir Shah, and then go to Southeast Asia.
While Washington officials have been quoted as saying they are "looking" for the right combination of credible, moderate leaders, Brahimi sees it differently. "We look forward to talking to as many Afghan parties as possible. What we need in the long run is a homegrown Afghan solution. No one wants an arrangement imposed on the Afghans."
The current UN vision of its role in this vexing country, once military action ends, is not as nation-builder, but as facilitator, offering everything from economic aid to help building infrastructure. Unlike missions in, say, Kosovo and East Timor, Afghanistan is not a new entity that needs to be built from scratch.
"In Afghanistan, we assume the nation exists, but is having a really tough patch holding itself together," says British Ambassador to the UN Jeremy Greenstock. "It's a question of getting the cogs working right again, and the engine needs to be changed. The UN can play the role of mechanic and engineer. But the Afghans have to drive the thing."
On the humanitarian end, the UN High Commission for Refugees, the World Food Program, and UNICEF are on the ground, dealing with a crisis that is mostly internal.
And legislatively, the UN Security Council on Sept. 28 passed Resolution 1373, which legally binds all member states to halt the support, financing, and harboring of terrorists. The resolution established a Counter-Terrorism Committee to ensure compliance. The CTC is offering help to any country short of the expertise or finances needed to improve their laws.
"Terrorism cannot be defeated in the long term, unless everybody subscribes to" the resolution, says Mr. Greenstock, who chairs the CTC. All countries have until Dec. 27 to turn in their initial reports on progress made. States that do not comply with 1373 will face at least diplomatic pressure, but perhaps even economic sanctions.
Meanwhile, as UN diplomatic efforts move forward, the world body resists calls to prepare peacekeepers for Afghanistan. Lessons seem to have been learned from places such as Somalia and Bosnia.
In Somalia, the UN learned the hazards of heavy-handed military action to separate warring clans, especially when the lead contingent, the Americans, quickly pulled out after 18 soldiers were killed in an ambush.
And in Bosnia, UN peacekeepers were neutral, not empowered with the ability to fight back or stymie aggression. When Bosnian Serbs breached the UN "safe haven" of Srebrenica and massacred some 7,000 Bosnian Muslim men and boys, the UN was forever tarnished.
In Afghanistan, there's speculation that if the Taliban is toppled, a sizable number of their fighters will go underground and adopt guerrilla tactics. So, there may not be true "peace" for peacekeepers to keep. Instead, there may be a need for "peace enforcers" - trained to kill if necessary.
"Afghanis are proud people who don't like strangers in their country, particularly strangers with guns," says a UN official in New York. "Any multinational force would have to anticipate casualties."