This is the text of the letter that Jacques Nasser, chief executive of Ford Motor Co., wrote to John Lampe, U.S. Bridgestone/Firestone Inc. chief executive, president and chairman, on Tuesday:

Dear Mr. Lampe: 

As you know, Ford has for many months been engaged in an intensive effort to determine the root cause of the tire failures that led to last summer's Firestone tire recall, and to prevent such failures in the future. Throughout this process, Ford has shared its findings and worked closely and cooperatively with NHTSA and with Firestone's technical team. 

Based on our work to date, we are concerned that the performance of certain Wilderness AT tires not included in last summer's recall is not at a level consistent with the performance of similar usage tires from competitive manufacturers. This concern rests significantly on data supplied by Firestone and NHTSA, which shows that failure rates for many of the Wilderness AT tires are already worse than competitive standards and may deteriorate further in the future. 

Our own laboratory and vehicle tests confirm these results. Although we have discussed our concerns with Firestone technical and management personnel, nothing we have learned has changed our view that the tires may present a risk to our customers' safety. 

Accordingly, we intend to announce an owner notification program to replace all Wilderness AT tires for our customers at no cost to them. This action is preventive in nature since we believe the significant risks are largely in the future. However, the data leave us convinced that this action is necessary to assure the safety of our customers, an objective that I know you fully share. 

As the replacement effort goes forward, let us work cooperatively to serve our customers and, most importantly, keep their safety as our highest priority. I hope this is a goal on which you can agree.