The diplomats, who are accredited to NATO, spoke on condition of anonymity because of the sensitivity of the discussions.

NATO's participation in any military action against Libya would require the approval of all 28 NATO members. But Turkish Foreign Ministry spokesman Selcuk Unal denied that his country was grounding NATO.

"Turkey is not blocking NATO, Turkey has been contributing to the preparations with a positive approach since the beginning," Unal told The Associated Press.

The NATO diplomats said the North Atlantic Council, NATO's top decision-making body, was unable to reach agreement Monday, and would take up the issue again on Tuesday for the fourth day in a row.

Even if such an order is adopted, it would take several days before aircraft under NATO command could start flying missions over Libya. The order also is likely to restrict NATO's air forces to making sure there are no unauthorized flights over Libya, with no mention of attacks on ground targets, one of the diplomats said.

Turkey was apparently not the only obstacle. Diplomats said France was seeking political leadership of the mission, but this was opposed by a number of other nations, which wanted NATO firmly in charge. Another sticking point was just how aggressive the enforcement of the no-fly zone should be, as several nations strongly opposed continuing the air strikes on Libyan ground targets.

Italy warned Monday that it would review the use of its bases by coalition forces if NATO does not take over. The country lies just across the Mediterranean from Libya and is allowing the use of seven of its military bases.

"Italy will begin reflecting on the use of its bases," said Foreign Minister Franco Frattini, according to Italian news reports. "If there is a multiplication of command centers, we must study a way in which Italy retakes control of its bases."

Italian Premier Silvio Berlusconi insisted the mission should pass to NATO's command, and said Italian planes would not launch any missiles. Speaking in Turin, he said coordination among partners must be "different from the one that has been established so far."

British Prime Minister David Cameron, however, praised the performance of the informal coalition, saying its forces had neutralized Libyan air defenses and helped avert a bloodbath.

The prime minister told British lawmakers that Gadhafi had violated a UN Security Council resolution by moving troops toward rebel-held cities and also had lied to the international community.

"Gadhafi responded to the UN resolution by declaring a cease-fire, but straightaway it was clear he was breaking that promise," Cameron said.

Cameron stressed that through airstrikes, coalition forces helped avert what could have been "a bloody massacre in Benghazi."

The aims behind coalition airstrikes - which Cameron called "necessary, legal and right" - were to suppress Libyan air defenses to enable the enforcement of a no-fly zone and to protect civilians.