Rebel fighters launch rockets during fighting against Muammar Gaddafi's forces at the frontline along the western entrance of Ajdabiyah April 21, 2011.[Photo/Agencies]

BAGHDAD - Coalition air strikes have degraded Libyan leader Muammar Gaddafi's main ground forces by 30 to 40 percent, but the battle appears to be heading to a stalemate, the top US military officer said on Friday.

"It's certainly moving towards a stalemate," said Admiral Mike Mullen, chairman of the US military's joint chiefs of staff, addressing US troops during a visit to Baghdad.

"At the same time we've attrited somewhere between 30 and 40 percent of his main ground forces, his ground force capabilities. Those will continue to go away over time."