But a build-up of U.S. troops last year allowed the military to focus a series of offensives against the group. The emergence of Sunni Arab tribal security units also helped to provide intelligence on al Qaeda activities.
URBAN STRONGHOLD
The result was that al Qaeda has largely been pushed out of Baghdad and its former stronghold in the western Anbar province to areas in northern Iraq, such as Mosul.
American generals say Mosul is al Qaeda in Iraq's last remaining urban stronghold in the country.
But U.S. commanders warn that the group, while significantly weakened, can still carry out large-scale attacks.
Iraq's Interior Ministry said last May that Masri had been killed, but soon afterwards al Qaeda released an audio tape purportedly from him.
And in an hour-long audio tape issued last month also said to be from him, Masri called for renewed attacks on American troops and lashed out at U.S. President George Bush.
He urged militants from the Sunni Islamist group to "celebrate" the recent announcement that the number of U.S. troops killed in Iraq had passed 4,000.
"We must celebrate this event in our special way, and make the defeated Bush join us in this celebration," he said.
He called on al Qaeda fighters to provide "a head of an American as a present to the trickster Bush" in a month-long campaign that he called the "Attack of Righteousness".
Al Qaeda in Iraq shares a name and ideology if not organisational ties with Osama bin Laden's network, which was blamed for the September 11, 2001 attacks on the United States.
The U.S. military says al Qaeda in Iraq is largely foreign led but that its foot soldiers are mainly Iraqis.
