"We do believe he is having some trouble in being able to mount a sustained campaign," said the U.S. official, speaking anonymously because he was discussing intelligence estimates. "That said, he is still much better organized than the rebels and still has the upper hand."
In some ways, Kadafi's forces have proved surprisingly adept. Instead of using armored troop carriers that attract attention from surveillance aircraft, they have camouflaged troop movements by relying on the same kind of battered pickup trucks that the rebels use, even disguising the vehicles with the opposition flag.
The concealment tactic on the ever-shifting front lines allowed Libyan army units to advance to the eastern city of Ajdabiya recently before they were beaten back for the third time by rebel troops and NATO air attacks. Yet again on Sunday, rebels in Ajdabiya came under attack from Kadafi's rocket-firing forces.
"We expected Kadafi to quickly fold his tent and go somewhere else," said Barno, a senior fellow at the Center for a New American Security, a Washington-based think tank. "But the Libyan forces quickly adapted to the airstrikes by becoming very quickly like civilians."
No one seems certain how to break the stalemate. Ratcheting down the NATO-led air campaign while large segments of Kadafi's military remain intact would leave the rebels vulnerable to being slaughtered.
The Air Force is flying two Predator drones over Libya to help conduct surveillance, but they are unarmed, officials said. The U.S. also is transferring precision-guided bombs to NATO allies flying combat missions, since supplies have begun running short, the NATO officer said.
The last time the United States undertook an air war largely for humanitarian purposes was during the 1999 NATO campaign in Kosovo, the Serbian province where police and soldiers loyal to Yugoslav leader Slobodan Milosevic were carrying out a ruthless assault on ethnic Albanians.
Clinton administration officials expected Milosevic to surrender quickly after NATO launched airstrikes, but the bombing campaign lasted 78 days. The Clinton White House promised early on not to send U.S. ground troops into Kosovo, but critics said that appeared to embolden Milosevic to resist.
Unlike the conflict in Libya, however, U.S. warplanes conducted the vast majority of the airstrikes during the Kosovo campaign and gradually escalated the bombing. U.S. officials even threatened at one point to begin flying attack helicopters, and Milosevic ultimately buckled.
There has been little sign that NATO is considering — or even capable of — that kind of escalation in Libya as long as the U.S. stays in a supporting role.
"By the U.S. taking a back-seat role, it has a psychological effect on the mission," said Dan Fata, a former Defense Department official who was responsible for overseeing NATO issues during the George W. Bush administration. "If I'm Kadafi, I'm thinking I can probably wait the Europeans out."
Cloud reported from Washington and Parker from Benghazi.