WASHINGTON – Iraqi insurgents are growing more effective and it takes time for the U.S. military to get its troops the protective equipment needed, defense officials said yesterday.

“This is not Wal-Mart,” one general said.

Officials also rejected growing criticism that armor shortages in Iraq reflect poor war planning, and they said they’ve been working as fast as possible to give troops what they need.

At a Pentagon news conference, Army officials declined to say how much has already been spent armoring vehicles for the campaign. But they said that in the next six to eight months, they will have spent $4.1 billion to try to make sure vehicles in Iraq and Afghanistan are those already manufactured with full armor or have had armor added to them.

They said they expect 98% of Army Humvees in theater to have proper armor by March and the rest of the fleet, such as fuel trucks, by summer.

“This is not Wal-Mart…this is a very detailed process in terms of trying to get this capability,” said Brigadier General Jeffery Sorenson, adding that it takes time to study, develop, test, and produce equipment needed against what commanders say is a sophisticated and ever-adapting enemy.

Asked at a separate news conference on Iraq operations whether he was concerned about still lacking protection, Lieutenant General Lance Smith said officials are concerned that insurgents have changed their tactics – attacking troops in the rear area after realizing they could not win in direct combat.

“Yes, we’re concerned that he has changed his tactics and it’s required us to armor vehicles that we might otherwise not armor,” he said of attacks on logistics convoys.

“I don’t know that we’ll ever find a silver bullet” against the insurgents’ homemade bombs, said General Smith, deputy commander of Central Command, which is responsible for U.S. military operations throughout the Middle East.

He said insurgents may use doorbell mechanisms today and remote controls from toys tomorrow to detonate the bombs that have become the major source of American casualties in Iraq.

“As we adapt, they adapt,” he said.

Generals Smith and Sorenson spoke to Pentagon reporters in two separate press conferences yesterday, a week after a soldier’s question to Defense Secretary Rumsfeld ignited a firestorm over why troops lack proper armor 21 months into the Iraq campaign.

Critics of Bush administration policies in Iraq blame what they say was a rosy picture the administration held before the war. The campaign was meant to be fought at rapid speed by a limited-size force with international help to disarm Saddam Hussein of his weapons of mass destruction. Instead, no weapons were found, the international community largely refused to participate, and officials have been forced to increase the size of the force there, now going up to 150,000 troops.

There was too little advanced body armor and too few armored vehicles to deal with what the Pentagon has since acknowledged is a far stronger and longer insurgency than expected, critics say. General Smith said all troops now have the body vests.

Defense officials say it wasn’t a matter of poor planning but that insurgents have proven very smart. American forces changed various tactics, including driving convoys fast through problem areas and getting jammers that foil insurgents’ ability to detonate bombs by remote control, General Smith said.

“And that’s been effective, but it’s effective for a short time,” General Smith said. “The enemy is very smart and thinking…so he changes his tactics and he becomes more effective.”

Officials also said this week that the Air Force has started making more cargo flights over Iraq to keep Army transport trucks off the country’s dangerous roads when possible.

“It’s not just armor…but a holistic approach” to the threat, General Sorenson said.