NATO officials said Wednesday that Moammar Gaddafi’s military has concealed its tanks, troops and weapons among civilians in Libyan towns to prevent NATO aircraft from carrying out strikes in support of rebel forces.

The accusation, by the French foreign minister and in a briefing in Brussels, came in response to rebel complaints that Western airstrikes have tapered off so much as to be ineffective since the United States turned over command of Libyan operations to NATO over the weekend.

In particular in Misurata, a besieged rebel-held city 130 miles east of Tripoli, Gaddafi’s forces have inflicted heavy casualties on civilians without being attacked by Western warplanes with the same intensity as before, rebel leaders said Tuesday.

French Foreign Minister Alain Juppe warned that the air campaign risked getting “bogged down” because of the Libyan tactics. In an interview on France Info radio, he said he would take up the issue with NATO commanders in an effort to restore the previous tempo of air operations.

But NATO officials said the reason for the slowdown around Misurata was a desire to avoid unintended casualties in areas where the Libyan military was cheek-to-jowl with civilian residents.

“We have confirmation that in Misurata tanks are being dispersed, being hidden, humans being used as shields in order to prevent NATO sorties to identify targets,” Brig. Gen. Mark van Uhm, NATO’s chief of allied operations, told reporters at NATO headquarters in the Belgian capital.

As the military conflict drags on, Libyan rebel leaders are beginning to prepare for the possibility that the country could end up divided in two.

In another development, French Defense Minister Gerard Longuet said rebels defending Misurata from now on will be able to receive ammunition and humanitarian relief supplies from Benghazi and other points by sea, apparently with Western warships assigned to protect the coastal sea lanes.

“We are going to ensure that aid comes from Benghazi and that at no moment Gaddafi’s forces will be able to stop this,” he said in a radio interview in Paris.

Benghazi is the rebels’ stronghold and de facto capital. On Tuesday, U.S. envoy Chris Stevens arrived there to meet with leaders and explore ways to find funding for their efforts.

Carmen Romero, the NATO deputy spokeswoman, said the increasingly desperate situation in Misurata is the top priority for NATO commanders directing the operations over Libya. Air cover for the rebels has gone on “unabated” since the United States turned over command, she told reporters, adding: “The ambition and the position of our strikes have not changed.”

Defense Secretary Robert M. Gates, in recent congressional testimony, said the United States would continue to provide aircraft for missions that other members of the coalition flying over Libya cannot field. Chiefly, he said, these are intelligence gathering, jamming and search and rescue.

In addition, U.S. officials have said other U.S. aircraft would remain on call if NATO commanders decide they need extra equipment.

But the pullback has meant U.S. aircraft that are particularly effective in providing close air support, such as the twin-jet A-10 Warthog and the AC-130 Specter gunship, are no longer deployed over Libya.