The US has expressed the hope that Libyan rebels have broken the military stalemate with forces loyal to Moammar Gaddafi, but stopped short Monday of predicting rebel victory after months of inconclusive battles. U.S. officials said they are encouraged by recent rebel advances near the capital of Tripoli and an apparent high-profile defection from Gadhafi''s inner circle. "It''s becoming increasingly clear that Gadhafi''s days are numbered," White House press secretary Jay Carney said, without elaborating on a weekend of significant advances by rebels from Libya''s western mountains toward Gaddafi''s stronghold of Tripoli. The rebels on Saturday pushed through to Zawiya, just 30 miles west of the capital on the Mediterranean coast, for the first time since the uprising against Gadhafi began in February. Gaddafi''s forces pushed rebels back from the center of Zawiya on Monday in fierce fighting to try to prevent the opposition from consolidating its gains. Neither Carney nor State Department spokeswoman Victoria Nuland said the rebels now have the upper hand. Nuland said the U.S. was watching with "considerable encouragement" the military progress of anti-Gaddafi fighters. She cited reports of the rebels taking of Gharyan and making advances in Zawiya and Tawargha, south of Misrata.