Troubled by political divisions within its ranks and a lack of firepower up front, Nato seems to have written off hopes of an early exit to the Libyan crisis and instead is aiming for a slow strangulation of Muammar Gaddafi's regime.
The 28 Nato countries showed unity at a meeting of foreign ministers in Berlin at the weekend, calling for Gaddafi's departure but failing to throw up any new ways of achieving this.
The rift among the allies is deep. France and Britain are shouldering the burden of the three-week-old Nato campaign but are barely restraining frustration at the lack of support from fellow alliance members.
The United States, scarred by its experiences of war in Afghanistan and Iraq, is now taking the back seat in combat operations. Italy, Libya's former colonial power, says it cannot join the strikes. Germany and Turkey are resolutely opposed.
On the ground, the situation is deadlocked. On the coastal strip, the only populated area in this desert country, Gaddafi's forces hold the centre, including the capital, Tripoli; the east is held by rebels although the front line is highly fluid; in the west, rebels hold a single city, Misrata, which is under brutal siege.
President Barack Obama implicitly acknowledged that the strategy was now long-haul.
"You now have a stalemate on the ground militarily, but Gaddafi is still getting squeezed in all kinds of other ways," Obama said. "He's running out of money. He is running out of supplies. The noose is tightening, and he is becoming more and more isolated. And my expectation is that if we continue to apply that pressure and continue to protect civilians, which Nato is doing very capably, then I think over the long term, Gaddafi will go and we will be successful. But again, it's only been three weeks."
Germany's Deputy Foreign Minister, Werner Hoyer, said Nato leaders "are now realising that this is not a very short mission. It takes much longer, it's much more complicated, it's much more demanding than some had expected."
Part of the problem is that Nato has so far been unable to muster the means to tip the balance, say analysts.
In the campaign's first phase, the United States, Britain and France unleashed standoff missiles to knock out Gaddafi's air force and communications. But they have been less successful in ground attack, which has enabled loyalist forces to regroup.
Only seven of Nato's members are actively participating in the air strikes. Other countries, along with the United Arab Emirates, Qatar and Jordan, have contributed planes to patrol a UN-backed no-fly zone but do not take part in attacks on the ground. Since the end of March, more than 800 strike missions have been flown, but only three have been conducted by the United States, which is otherwise carrying out a supporting role, in airborne intelligence, jamming and refuelling.
This tally of missions is misleading, said Paul Smyth, a retired Royal Air Force wing commander who runs a consultancy, R31 Consulting.
"Tracking sortie numbers is not the number of aircraft flown, but the time spent on a given task," he said. "The official Nato sortie figures suggest that more strike assets are required."
Smyth also doubted Nato had "the ideal mix" of planes to enable it to both carry out air patrols and suppress forces on the ground. In Berlin, Nato Secretary-General Anders Fogh Rasmussen called on the allies to contribute another 10 aircraft, but did not spell out which kind.
The strains have shed light on the capacity of Britain and France to prosecute the campaign without a US lead and support from Italy and Germany, the only other European countries to have significant armed forces.
A report by a panel of MPs in Britain last week said the Typhoon, a brand-new and massively expensive interceptor built by four European countries, had been hit by shortage of spare parts that meant only eight out of 48 RAF pilots had been trained for using it for ground attack.
The European countries are even running short of laser-guided "smart" bombs needed to precision-target Gaddafi forces in urban areas, the Washington Post reported. They also lack specialised ground-attack planes, such as the AC-130 gunship which peppers areas with heavy machine-gun rounds.
The US is holding these planes in reserve but said they were available if Nato commanders requested them.
Among possible options for Nato are more use of armed drones, if any can be spared from Afghanistan, opening up a protected sea corridor to Benghazi in the east and Misrata in the west and providing weapons to the rebels, say analysts.
"The risk is that jihadists may fill the political void that has opened up in the east of the country.
"We saw this in Iraq and we saw it in Yemen. So I think we will be careful about shipping any arms to the rebels," said Denis Bauchard, a former French ambassador in Jordan and now an adviser at the French Institute of International Relations for the Middle East.By Catherine Field Email Catherine