NATO ambassadors decided late Sunday to take over control of all UN-mandated military operations in Libya, including any air strikes that are carried out to protect civilians from embattled leader Muammar Gaddafi's troops.
The military alliance had earlier already agreed to implement two other UN mandates - enforcing a no-fly zone over the North African country and patrolling an arms embargo in the Mediterranean.
Ambassadors from the 28 member states Sunday decided that NATO should also implement the mandate of taking "all necessary action" to protect civilians from attacks.
"NATO will implement all aspects of the UN resolution. Nothing more, nothing less," Secretary General Anders Fogh Rasmussen said in a statement. "This is a very significant step, which proves NATO's capability to take decisive action."
He added that NATO's top operational commander has been instructed to start executing the civilian protection operation "with immediate effect".
That mandate had so far been implemented by an 11-member international coalition led by the US. It has used air strikes to take out Libyan air defences and ground forces in order to prevent attacks on civilians.
Turkey, NATO's only predominantly Muslim member, had previously been reluctant to let the military alliance take on the third mandate, as its leaders said they did not want to be involved in bombing a fellow Muslim country.
But NATO Group Captain Geoffrey Booth noted this week that "the majority of those (targeted attack) missions appear to have been successful and therefore I would assume close to completion".
NATO members now have to decide if and how they want to participate in the operation. So far, only Germany has ruled out an involvement in the Libya mission.
The operation is also expected to involve non-NATO members such as Sweden. It is set be run from NATO's air base in Izmir, Turkey, with overall command in Naples, Italy, which already supervises the naval embargo operations.
While military command will strictly remain within NATO, officials have said that an international conference in London Tuesday will set "the wide political guidance" for action against Libya.
France, which has insisted on political oversight over NATO's operations in Libya, has said that it will propose a diplomatic solution jointly with Britain ahead of the London conference.
The political oversight is in part designed to appease Arab nations who have supported the no-fly zone. Qatar and the United Arab Emirates have so far been the only Arab countries to actively join the international military action by contributing jets.