Adam Gadahn, known as Azzam the American, in a 17-minute video said al-Qaida has "condemned and continue to condemn" attacks by the West or other "secular political forces," CNN International reports.
The FBI includes Gadahn on its list of most-wanted terrorists for his alleged role and material support for terrorist activities.
Gadahn, meanwhile, said al-Qaida viewed those civilians killed in the conflicts in Pakistan and Afghanistan as martyrs.
"We express our condolences to the families of the Muslim men, women and children killed in these criminal acts," he said in the video. "And we ask Allah to have mercy on those killed and accept them as shohadaa (martyrs)."
His comments come as U.S. Navy Adm. Mike Mullen, the chairman of the Joint Chiefs of Staff, arrived Monday in Kabul on an unannounced visit with American forces as they prepare for the next phase of battle.
U.S. President Barack Obama on Dec. 1 pledged 30,000 additional troops to Afghanistan as part of a revised war strategy. Mullen said some troops could head to Afghanistan as early as this week.
Gadahn in his video message did not address the surge specifically. Instead, he warned nations that made the "foolish decision" to support the war effort that they would have "the blood of countless Muslims" on their hands.