Ford Motor Co., launching the latest salvo in its battle with General Motors Corp. for light truck dominance, is upping discounts on its largest and most profitable sport-utility vehicles. Ford told dealers that beginning July 3 rebates on the full-size Expedition will be increased $500 to $2,000. The automaker is upping the discount on the Excursion by $1,000 to $2,500, as well as offering cheaper financing rates. The sweetened incentives come after Ford pledged to its dealers that it would beat back GM's truck offensive. In the first half of 2001, Ford lost ground to GM in the crucial large SUV market.