Brahimi ruled out a UN peacekeeping force
An administration run by Afghans from home and abroad "would be far more credible than one run by UN officials parachuted in," said Mr Brahimi.
He said he hoped to start the complex procedure of forming a broad-based government "as soon as humanly possible".
Security force
But the UN envoy warned that without "genuine and lasting" security a new government would be meaningless.
He told the Security Council there were three options for a security force:
Mr Brahimi said his deputy, Francesc Vendrell, would go to Kabul as soon as security conditions allowed and other UN staff would follow in a day or so.
The UN is anxious to step up the delivery of aid in the country, where the shipment of crucial supplies has been disrupted during the US air strikes.
Mr Brahimi suggested a meeting between the Northern Alliance, which controls much of the north of Afghanistan and Kabul, and the nation's many other ethnic and tribal groups to agree on a framework for a political transition.
Devil in the detail
He said that there is widespread agreement among the Afghan parties on the principle of a broad-based government, but the difficultly was agreeing on the details.
This meeting would then decide how to convene a provisional council, which would be chaired by "an individual recognised as a symbol of national unity".
This could be an allusion to Afghanistan's exiled King, Mohammad Zahir Shah, who currently lives in Rome.
The provisional council would plan a two-year transitional administration and during that period a loya jirga, or grand council of prominent Afghans, would prepare a constitution - which would be approved by a second loya jirga - for a permanent Afghan government.
Noting that the Afghan people have been failed many times in the past, Mr Brahimi promised: "We are not going to give up on them this time."
Funding
The envoy called for a trust fund to organise the finances needed to restore the devastated country, which needs not only reconstruction and rebuilding, but the creation of political institutions.
While pressure is building for the UN to find a political solution for Afghanistan, UN Secretary General Kofi Annan said the country presented the organisation with one of its greatest challenges. He urged the international community to be ready to respond.
Earlier, the United Nations High Commissioner for Human Rights, Mary Robinson, had expressed concern for Afghan civilians in cities falling to the Northern Alliance.
"When territory has changed hands in recent years in Afghanistan, there has been a terrible massacre of civilians, raping of women, a retaliatory sort of destruction by whoever comes in to take a town or a city," she told reporters at a human rights conference in Delhi.