Defense Secretary Robert Gates is creating a department-wide task force to focus on ways to counter the roadside bombs that have caused 80 percent of U.S. casualties in Afghanistan.

The challenges are different from those in Iraq, Gates told reporters Thursday before a visit to a Wisconsin factory that is producing a rugged new armored vehicle for use in Afghanistan. He said most of the improvised explosive devices, or IEDs, in Iraq are based mainly on artillery shells and are triggered electronically. Those in Afghanistan, he said, are made primarily from fertilizers such as ammonium nitrate, with mines as detonators.

He also pointed out that Afghanistan's terrain is different, its road system is different — streets running from paved to unpaved to nonexistent — and the bomb builders' networks are structured differently than in Iraq.

"I have decided I need to focus my attention on this problem," he said.

Gates has recently expressed concern about whether the Pentagon groups working on the threat — the Joint IED Defeat Organization, the intelligence community and the commanders in the field — are properly integrated and sufficiently flexible. JIEDDO is the multibillion-dollar agency set up to lead and coordinate the Defense Department's efforts against roadside bombs.

Two weeks ago, however, the Government Accountability Office criticized the agency for not having a database that includes both its own projects and those being carried out independently by the individual services. In addition, the GAO said, JIEDDO "lacks a means as well as reliable data to gauge the effectiveness of its counter-IED efforts," according to its Oct. 29 report to the House Armed Services subcommittee on oversight and investigations.

To head the new task force, Gates chose Ashton Carter, the undersecretary of defense for acquisition, technology and logistics, and Lt. Gen. John Paxton, the Joint Staff's director of operations. Calling this one of his top priorities for the next six months, Gates said he would meet monthly with the group.

The secretary also offered some ideas of his own. Referring to a recent seizure in Afghanistan of a big cache of illegal ammonium nitrate, he said that the law has not been enforced up to now and that the goal is to get such substances under control. He added: "If we have to pay for some of it, I'm open to that."

Gates also recommended looking back to the 1980s, when some of the Afghans who are fighting today as Taliban insurgents were, with CIA assistance, using similar IEDs against the invading Soviet Union.

"So let's go back and look at the playbook that they used against the Soviets to see if there's something that we could learn in terms of adapting our tactics, techniques and procedures," he said.