Moammar Gadhafi's troops launched a powerful assault with tanks and rockets Friday on Misrata, the last major rebel city in western Libya, sending residents fleeing to increasingly crowded safe areas of the city that are still out of the Libyan leader's reach.

Misrata has become emblematic of the limits of NATO's air campaign, with the alliance's top military commander saying he needs more precision attack aircraft to avoid civilian casualties in urban combat. President Barack Obama acknowledged in an interview that the two-month-old civil war has reached a stalemate.

After a weeklong flurry of high-level diplomatic meetings in Europe and the Middle East, rebel leaders complained that the international community is not doing enough to keep Gadhafi's troops at bay.

Friday's attacks on Misrata — even as NATO foreign ministers meeting in Berlin debated handling of the Libya air campaign — highlight rebel worries that international intervention won't come fast enough or will be ineffective.

"Time is critical, especially for the people in the west part of the country, especially in Misrata," said Mustafa Gheriani, a spokesman for the rebels who seized much of eastern Libya from Gadhafi at the start of the war. "Is there something else on the diplomatic ground that they know that we don't to put more pressure on Gadhafi? The guy is still shelling and killing and it makes no difference to him."

Rights groups have warned that the situation in Misrata, Libya's third-largest city, is dire after 50 days of siege by Gadhafi's troops. Hospitals are unable to cope with growing numbers of casualties, including many shrapnel injuries.