As many as 20,000 insurgents?

BAGHDAD, Iraq — The Iraq insurgency is far larger than the 5,000 guerrillas previously thought to be at its core, U.S. military officials say, and it's being led by well-armed Iraqi Sunnis angry at being pushed from power alongside Saddam Hussein.

Although U.S. military analysts disagree over the exact size, dozens of regional cells, often led by tribal sheiks and inspired by Sunni Muslim imams, can call upon part-time fighters to boost forces to as high as 20,000 — an estimate reflected in the insurgency's continued strength after U.S. forces killed as many as 4,000 in April alone.

And some insurgents are highly specialized — one Baghdad cell, for instance, has two leaders, one assassin, and two groups of bomb-makers.

The developing intelligence picture of the insurgency contrasts with the commonly stated view in the Bush administration that the fighting is fueled by foreign warriors intent on creating an Islamic state.

"We're not at the forefront of a jihadist war here," said a U.S. military official in Baghdad, speaking on condition of anonymity.

The official and others told The Associated Press the guerrillas have enough popular support among nationalist Iraqis angered by the presence of U.S. troops that they cannot be militarily defeated.

The military official, who has logged thousands of miles driving around Iraq to meet with insurgents or their representatives, said a skillful Iraqi government could co-opt some of the guerrillas and reconcile with the leaders instead of fighting them.

"I generally like a lot of these guys," he said. "We know who the key people are in all the different cities, and generally how they operate. The problem is getting actionable information so you can either attack them, arrest them or engage them."

Even as Iraqi leaders wrangle over the contentious issue of offering a broad amnesty to guerrilla fighters, the new Iraqi military and intelligence corps have begun gathering and sharing information on the insurgents with the U.S. military, providing a sharper picture of a complex insurgency.

"Nobody knows about Iraqis and all the subtleties in culture, appearance, religion and so forth better than Iraqis themselves," said U.S. Army Lt. Col. Daniel Baggio, a military spokesman at Multinational Corps headquarters in Baghdad. "We're very optimistic about the Iraqis' use of their own human intelligence to help root out these insurgents."