BRUSSELS -- On a day when Libyan leader Moammar Gadhafi's forces again launched withering attacks against rebels using warplanes, tanks and artillery, U.S. officials and foreign diplomats said Wednesday that the carnage hadn't reached a tipping point necessary for a Western military response.

Beginning today, NATO defense ministers will meet for two days in Brussels, to determine whether to impose a no-fly zone to stop Col. Gadhafi's air attacks. Some Arab states in recent days have backed imposing a no-fly zone, but there is no consensus, and such a plan could take some time to implement.

Western officials have expressed concerns that a no-fly zone would not turn the tide of the fighting. But diplomats said that if the Libyan government escalates attacks on civilians, there is strong support for such a move in many NATO capitals.

The Obama administration and its allies prefer to first get the blessing of the U.N. Security Council. But they may be willing to endorse the step without it, provided there is support from such organizations as NATO, the Arab League and the African Union. U.S. and European officials fear that without such support, any Western-led intervention could provoke a negative reaction in Arab nations.

It's unlikely that NATO will reach a decision in the meetings on a no-fly zone, said diplomats who spoke on condition of anonymity about the sensitive discussions. France has said it will not support such a mission without Security Council approval, but permanent members China and Russia are balking. Opposition also remains in Turkey, and German officials have told other officials privately that they, too, are opposed to it, the diplomats said.

There have been mixed signals from the Arab League, with some members saying they welcome a no-fly zone, and others, including Algeria and Syria, against it. Syrian officials privately have indicated they may be willing to yield, the diplomats said.

Also up for discussion at NATO is whether to provide humanitarian aide by air or sea to rebel-held towns near the borders with Egypt and Tunisia. Western countries are eager to approve those steps, and diplomats said they expect there will be announcements of additional help soon.

U.S. Defense Secretary Robert M. Gates is among the officials attending the NATO meetings. Mr. Gates, who has expressed concerns about U.S. military action against Col. Gadhafi, is not opposed to using force but wants to explore the potential consequences of intervening, his spokesman said Wednesday.

First Published: March 10, 2011, 5:00 a.m.