BRUSSELS – Despite pressure from some NATO allies to halt the bombing in Libya, U.S. Defense Secretary Leon E. Panetta said Thursday that alliance warplanes will keep flying as long as combat persists between the provisional government’s fighters and forces loyal to deposed leader Moammar Gadhafi.

“If there continues to be serious fighting, if there continues to be threats to the civilian population, then I’m sure this mission will continue,” Panetta told reporters after two days of meetings with defense chiefs and military commanders at NATO headquarters here.

During the talks, U.S. and French officials pushed to sustain the air war at least until the government’s forces capture Sirte, Gadhafi’s birthplace. The officials warned that stopping the airstrikes before the city falls could encourage pro-Gadhafi forces, who are waging an increasingly desperate battle to hold the coastal enclave.

Other NATO members privately urged a quicker halt to the operation, arguing that the alliance in effect had achieved its stated mission of protecting Libyan civilians even if fighting continues in scattered pockets.

Some nations are worried about the mounting expense of the air war, which began March 19. But those concerns were largely papered over in public this week.

Panetta said a decision to halt the NATO operation, which also includes enforcing a “no-fly” zone and a naval blockade along the Libyan coast, would come only after senior military commanders recommend doing so.