NATO will depend on Europe’s aerial firepower to keep up momentum in the mission to protect civilians in Libya when the US military withdraws into a backup role later Monday, officials said.

The United States has conducted half of around 70 daily air bombing missions against Moamer Kadhafi’s ground forces during the campaign, but US fighter jets will pull out of the frontline within hours, NATO officials said.

US President Barack Obama, whose troops are already facing the brunt of the fighting in the NATO-led war in Afghanistan, has been in a hurry to wind down US operations in Libya and move to a support role to the 28-nation alliance.

The US military had planned to stop its air missions and Tomahawk missile launches at the weekend but it accepted a NATO request to continue the operations for another 48 hours until Monday.

“To make up for the American assets that will leave, the other countries will have to multiply their sorties and open up more ammunition,” a military official told AFP.

Since NATO took command of operations on March 31, alliance warplanes have conducted 276 strike missions, although planes did not necessarily drop their payload during every flight, according to official figures.

“The NATO mission, which is to protect civilians, remains the same, regardless of the role of this or that ally, however big it may be,” a NATO diplomat said.

Before NATO took over, the United States led the international coalition along with France and Britain that began bombing Libyan tanks and artillery in a UN-mandated mission to protect civilians from the regime.

The Libyan army’s fixed installations were obliterated by US Tomahawk missiles that rained down on the regime in the first 10 days of the operation, the military source said.

After the United States withdraws around 40 attack planes, NATO can count on scores of jets from other member nations to continue the ground strikes. The US will provide surveillance, jamming and refuelling aircraft instead.

“We are quite confident that we have the flexibility and depth of contributions to adjust despite the fact that the US is changing its force posture,” a NATO official said.

With around 20 and half a dozen attack planes respectively, France and Britain will likely carry the bulk of the load after US jets are grounded.

French jets have conducted between a fifth and a quarter of daily sorties, while the British have taken part in one in 10 missions, a NATO diplomat said.

The head of the Royal Air Force (RAF), Air Chief Marshal Stephen Dalton, told The Guardian newspaper that British warplanes are likely to play a role in the no-fly zone over Libya for at least six months.

The five other nations participating in bombing missions — Belgium, Canada, Denmark, Italy and Norway — use around 30 warplanes in total.

More NATO nations are taking part in two other missions, policing a no-fly zone to prevent Kadhafi’s warplanes from flying and an arms embargo to stop suspect ships from bringing weapons and mercenaries into Libya.

“Every ally, in particular those who take part in few strikes, will have to pick up the tempo,” the military official said.