official said more discussion was needed on another plan for possible NATO involvement in enforcing a U.N. no-fly zone over Libya.
Alliance member Turkey, which has spoken against intervention in Libya, had earlier blocked agreement among the ambassadors, a NATO diplomat said.
The envoys from the 28 NATO nations will have to meet again to agree to implement the plan for enforcing the arms embargo
, which would involve use of alliance aircraft and ships to prevent weapons reaching Libyan leader Muammar Gaddafi
Several NATO nations, led by France, Britain and the United States, have taken part in air attacks on Libya launched on Sunday; but NATO as an organization -- which takes all decisions by consensus -- has been divided on whether to take part.
Germany has also spoken against foreign intervention in Libya and diplomats said France had argued against NATO involvement, citing the alliance's reputation in the Arab world as a result of the war in Afghanistan and given that it was seen as being dominated by the United States.
Diplomats said Britain, the United States and Canada were among those alliance states wanting NATO to take a lead in Libya. The alliance's role is currently limited to air surveillance.
Earlier on Sunday, U.S. Defense Secretary Robert Gates stressed the limits of planned U.S. military involvement in Libya, despite the heavy assault on Gaddafi's forces.
He said the United States would not have a "preeminent role" in the anti-Gaddafi coalition that will maintain a no-fly zone, and expected to turn over primary responsibility for the mission to others within days.
He said Britain or France could take charge of the air operation, or NATO could lead, if sensitivities among the Arab League over working under the Western alliance leadership were assuaged.