TRIPOLI, Libya – Britain is sending up to 20 military advisers to help Libya's ragtag rebel force break a military stalemate with Moammar Gadhafi's army, even as NATO acknowledges that airstrikes alone cannot stop the daily shelling of the besieged opposition-held city of Misrata.

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Gadhafi's troops have been pounding Misrata indiscriminately with mortars and rockets, a NATO general said Tuesday, and residents reported more explosions and firefights in Libya's third-largest city. Hospitals are overflowing and 120 patients need to be evacuated from the city that has been under siege for nearly two months, the World Health Organization said.

The plight of Misrata's civilians and the battlefield deadlock are raising new questions about the international community's strategy in Libya. The leaders of the US, Britain and France have said Gadhafi must go, but seem unwilling to commit to a more forceful military campaign. NATO's mandate is restricted to protecting civilians.

Adm. Giampaolo Di Paola, chairman of NATO's military committee, said that even though the military alliance's operations have done "quite significant damage" to the Libyan regime's heavy weaponry, what Gadhafi has left is "still considerable."

Asked if more airpower is needed, Di Paola said any "significantly additional" allied contribution would be welcome.

The rebels seized control of most of eastern Libya shortly after the uprising began in February, while Gadhafi is entrenched in the west, but the front line hasn't changed dramatically since then.

Frustration over the stalemate has spurred talk in the West of new tactics, including dispatching military personnel to Libya.

Britain took the lead Tuesday, saying it is sending up to 20 senior soldiers who will help organize the rebels, many of whom have had little military training or battle experience. However, British Foreign Secretary William Hague said Britain would not arm the opposition or assist in military operations.

Britain has already sent non-lethal support, including 1,000 sets of body armor and 100 satellite phones.

"As the scale of the humanitarian crisis has grown, so has the urgency of increasing our efforts to defend civilians against the attack from Gadhafi forces," Hague said.