By Matt Spetalnick and David Brunnstrom
BERLIN (Reuters) - NATO allies rebuffed on Thursday French and British calls to contribute more actively to the air war in Libya despite fears of a military stalemate.
U.S. Secretary of State Hillary Clinton told NATO ministers meeting in Berlin it was vital for NATO to maintain "resolve and unity" against Libyan leader Muammar Gaddafi but gave no hint Washington was prepared to re-engage in ground strikes.
As they met, a spokesman for the anti-Gaddafi rebels besieged in the western city of Misrata warned of an impending government "massacre" unless NATO intervened more decisively. The rebels said 23 civilians were killed in a rocket attack on a residential zone near Misrata port on Thursday.
U.S. officials, briefing on condition of anonymity, appeared to brush aside French and British complaints about the pace of air strikes, saying NATO commanders had not sought more resources.
Spain said it had no plan to join the seven NATO states that have been involved in ground strikes, while Italy, the former colonial power in Libya, said it would need to hear convincing arguments for it to do so.
"As far as NATO is concerned, we have the forces that we need," one U.S. official said, as the NATO ministers discussed the air campaign with Arab countries and other states that have joined the NATO-led effort in Libya.
"If the commanders feel they need more capability, they will ask for more capability. That's not what they're doing ... there is not a demand from the commanders for more."
French Defense Minister Gerard Longuet said this week that Gaddafi's attacks would not be stopped without U.S. participation in strikes on his tanks and artillery, which ceased after NATO took command of Libyan operations on March 31.
NATO SAID SHORT OF AIRCRAFT
Britain, France and Denmark are carrying out most of the ground strikes.
A NATO official said on Wednesday the alliance was still short of about 10 aircraft a day to conduct air strikes. A French official named Italy, Spain, the Netherlands and Sweden as countries that could do more to assist operations.
The French official said greater U.S. involvement would help as European air forces conducting ground strikes lack low-flying A-10 "tankbuster" planes and AC-130 gunships that analysts say would be useful against Gaddafi's forces.
On Wednesday, the Pentagon said U.S. warplanes had continued to strike Gaddafi's air defenses even after NATO took over Libya operations, but targeting his tanks and artillery is now key.
One NATO diplomatic source said there were three ways the alliance could increase combat aircraft capability.
Countries already contributing aircraft could reconfigure interceptor planes enforcing the no-fly zone to be able to carry out ground strikes or they could change the mix of aircraft they have deployed, sending more combat planes instead of interceptor aircraft, the source said.
The third option, seen as the most difficult, was to persuade new countries to join the operation.
The source said alliance members must back up their commitment to the Libya operation with firepower. "You can't sign NATO up to do something and then not provide all of the means it needs to do this over the medium term," he said.
Spanish Foreign Minister Trinidad Jimenez said had decided at the start of the mission to provide ships and planes to implement a U.N.-mandated arms embargo and the no-fly zone.
"This is the Spanish contribution now and it will be the Spanish contribution in the future," she said.
Italian Foreign Minister Franco Frattini said Rome would consider any request by Libyan rebels for its forces to open fire, but needed to consider its colonial past in the country.
"Italy has apologized to the Libyan people for the horrors committed during the period of fascist colonization, so if civilian casualties were caused by any bombing operations it would be an extremely serious thing," he said.
Frattini said Mustafa Abdel Jalil, head of the rebel Provisional Transitional National Council, would meet Prime Minister Silvio Berlusconi in Rome on Friday. "If the Libyans give us strong arguments, we will see, the government will decide," he told daily Il Sole 24 Ore in an interview.
Rome has contributed air bases and eight aircraft to the NATO mission, but they have only taken part in reconnaissance and monitoring operations.
U.S. officials said the main focus on the Berlin talks would be to define precisely what the alliance is trying to achieve with the military campaign.
They gave no sign of any emerging consensus among the allies on whether to start arming the rebels, but reiterated Obama's assertion that he "hasn't ruled it out and hasn't ruled it in."
(Additional reporting by Adrian Croft; editing by Paul Taylor)