The alliance took over from Germany and the Netherlands, which have jointly led the International Security Assistance Force, known as ISAF, since Feb. 10.
"ISAF's name and mission will not change," said NATO Deputy Secretary General Alessandro Minuto Rizzo. "But what will change as of today is the level of commitment and capability NATO provides."
The outgoing commander, German Lt. Gen. Norbert van Heyst, handed over control during a formal ceremony in an auditorium inside the capital's Amani High School. The new commander, NATO Lt. Gen. Gotz Gliemeroth, who is also from Germany, accepted a green flag from Van Heyst to mark the change. Gliemeroth's deputy will be Canadian Maj. Gen. Andrew Leslie.
The school auditorium was ringed by scores of armed peacekeepers and ISAF armored cars mounted with machine guns. Bomb-sniffing dogs were on hand to search for any explosives.
Present were President Hamid Karzai, German Defense Minister Peter Struck, NATO's Supreme Allied Commander Gen. James L. Jones and a host of diplomats and U.N. officials.
Struck said in a speech that the handover showed the world's commitment to rebuilding war-shattered Afghanistan.
"Afghanistan must not lapse back into anarchy and chaos and must not again become the home of global terror, as was the case under the rule of the Taliban," Struck said.
"What the people of Afghanistan wish for is a stable peace. They are pinning great hopes on the international community. The support of NATO for ISAF... is a visible expression of the fact that the people of Afghanistan will not be let down."
NATO is taking over command in large part to end the arduous task of searching for a new "lead nation" every six months to run ISAF.
NATO spokesman Mark Laity told reporters in Kabul on Sunday that a single, open-ended command by NATO would add more continuity to the mission as well as an institutional memory. Most commanders, after learning the intricacies of Afghanistan, have been rotated out after six-month tours-of-duty.
ISAF will continue operating exactly as before, with the "same mission, same mandate, same banner," he said.
The 30-nation force was created in December 2001 to bolster security in Kabul in the wake of the U.S.-led war that toppled the Taliban, which had granted haven to Osama bin Laden's network.
About 90 percent of ISAF's troops are from NATO countries, though 15 of the 30 contributing countries are — and will still be — from non-NATO nations, said German peacekeeping spokesman Lt. Col. Thomas Lobbering.
The deployment in Asia will be NATO's first outside Europe since the organization was formed during the Cold War to provide a bulwark against possible attacks by the former Soviet Union.
"NATO is a defensive alliance and it still is. But previously how you defended yourself was defined by parking your tanks along your borders and preventing the former Soviet Union and its allies crossing," Laity said.
"What we saw on Sept. 11 was that the most powerful member of the alliance was attacked by a threat which emanated from Afghanistan. So the traditional concept of defense needed to be revised," Laity said.
NATO will face the same challenge other lead nations have in the past: ensuring stability in Kabul and preventing possible terrorist strikes. ISAF suffered its worst-ever hostile casualties in June, when a suicide attacker driving an explosives-laden taxi killed four German peacekeepers and wounded 29 others.
Despite such threats, the capital is considered a safe island in a sea of insecurity. Much of Afghanistan is ruled by rival warlords whose armed factions frequently turn their guns on each other. A vast area along the southern and eastern border with Pakistan, meanwhile, is home to a low-level guerrilla insurgency being waged by Taliban rebels and their allies.
Karzai's government has repeatedly called for ISAF's mandate to be expanded outside the capital, particularly with general elections due in June 2004.
So far, however, no nation has been willing to support that endeavor, which would require at least 10,000 additional troops.
NATO currently leads other peacekeeping forces in Kosovo and Bosnia.