It may be too soon to celebrate the recent gains made by the Libyan rebels: The U.S. military warns that they could be rolled back quickly without continued air support. “The regime still vastly overmatches opposition forces militarily,” warned Gen. Carter F. Ham, the ranking American in the coalition operation. Furthermore, there’s little sign that Gaddafi loyalists are defecting. Ham’s statement comes as the rebels approach the coastal city of Sirte after retaking the towns of Brega and Ras Lanuf without resistance over the weekend. Meanwhile, Gaddafi’s forces continue to lay siege to the rebel-held city of Misrata despite allied airstrikes.