Abu Hamza al-Muhajir, also known as Abu Ayub al-Masri, said in an audio recording posted on the internet on Friday that the group had 10,000 others waiting to be equipped.
"The al-Qaeda army has 12,000 fighters in Iraq, and they have vowed to die for God's sake," said al-Muhajir in the recording whose authencity has not been independently verified.
He also pledged his allegiance to a new Islamist state in Iraq and its leader, who he said was Abu Omar al-Baghdadi.
In October, an Iraqi group that includes al-Qaeda in Iraq has announced that it has established an Islamic government in Iraq that consists of several provinces, including Baghdad, that have large Sunni populations.
Al-Muhajir also gloated over the resignation of Donald Rumsfeld, the US defence secretary.
He said: "I tell the lame duck [US administration] do not rush to escape as did your defence minister...stay on the battle ground."