Coalition air strikes have degraded Libyan leader Muammar al-Qaddafi's main ground forces by 30 to 40 percent, but the conflict is becoming deadlocked, the top U.S. military officer said on Friday.

"It's certainly moving towards a stalemate," said Admiral Mike Mullen, chairman of the U.S. military's joint chiefs of staff, addressing U.S. 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."

Mullen, who arrived in Baghdad on Thursday for talks with Iraqi leaders and to visit U.S. troops, said the international consensus was that "Gaddafi's gotta go." But he acknowledged it was unclear how long it might take for that to happen.

"Every single action that countries are taking ... are going to continue to put the squeeze on him until he's gone. Is he going to figure that out? I don't know," Mullen said.

Mullen said there was no sign of al Qaeda representation in Libya's opposition, playing down concerns about any militant groups edging their way into the Libyan conflict.

"It certainly doesn't mean, whether it's Libya or in other countries that there aren't leaders in terrorist organisations that aren't looking to try to take advantage of this," Mullen said.

"But we're watchful of it, mindful of it and I just haven't seen much of it at all. In fact, I've seen no al Qaeda representation there at all."

Mullen acknowledged that the Libyan Islamic Fighting Group [LIFG], which waged a failed armed insurgency against Gaddafi's rule in the 1990s, had "stirred a little bit."

"But I haven't seen anything significant at this particular point in time," he said.

The LIFG represented the greatest challenge to Qaddafi in the 90s and made several failed attempts to assassinate the Libyan leader.