The U.S. government blames Firestone tires, not Ford Explorer SUVs, for those rollover accidents involving Explorers riding on Firestone tires that shredded in hot climates.

Tread separation on an Explorer is “no more likely to lead to a crash than other SUVs,” according to the National Highway Traffic Safety Administration.

Many Firestone Wilderness AT tires built before 1998 contain a safety defect, says the agency. It ordered Bridgestone/Firestone to recall 3.5 million more tires. That’s in addition to a recall of 6.5 million Firestone tires in August 2000.

The agency links 271 fatalities to rollover accidents involving Firestone tire failures. Bridgestone/Firestone had claimed that Explorer design flaws caused the rollovers.

``At this point, NHTSA does not agree with Firestone’s claim that Explorers are more prone to rollover after tread separation,'' a U.S. Department of Transportation official says. ``NHTSA found no basis for the Firestone allegations.''

Bridgestone/Firestone CEO John Lampe disputed the NHTSA report. A Ford Motor Co. spokesman says it vindicates the automaker and confirms Ford’s own tests.

Ford had replaced millions of Firestone tires on Explorers, sales of which suffered as the controversy grew. Ford and Firestone this year ended their long-standing business relationship as each tried to deflect the heat onto the other.

The NHTSA says Firestone made changes in the Wilderness AT tire design in 1998 but “because tread separation failures rarely occur in these tires until at least three years of use, NHTSA cannot determine whether their actual field performance is significantly better than the older (recalled) tires.”

The NHTSA says it will continue to monitor the field performance.

Ford has already replaced more than six million Wilderness AT tires – about half the total number still on its customers' vehicles.

Ford will not use Firestone Wilderness AT tires in its replacement program. If customers insist on those tires as replacements, they’ll be directed to Firestone stores.

Firestone faces hundreds of lawsuits over the tire fiasco. It has already settled about 1,000 cases.

(More information about the NHTSA report is at )