DETROIT  —  General Motors Corp. (GM) said Tuesday it was now offering cash rebates totaling up to $2,500 on some of its 2005 model vehicles, in another escalation of Detroit's incentives war.

The world's largest automaker also cut the basic cash rebate on most of its 2004 model cars and trucks by $500, to $3,500 and $4,500 respectively, GM spokeswoman Deborah Silverman said.

Customers financing their purchase of a 2004 model through GM's finance arm would also be eligible for an additional "bonus cash" offer of between $500 and $1,500, Silverman said.

The bonus cash program varies by region of the country and by model, she said. But in some cases, consumers could get a total cash rebate of up to $6,000 on vehicles from the 2004 model year.

The basic rebate on most 2005 cars and trucks, which are just now making their way into dealership showrooms, is $1,000. Model year 2005 Cadillacs and Hummers have no cash rebate incentives, she said.

But on a limited number of number of 2005 models, she said customers financing through General Motors Acceptance Corp. (search) could walk away with a rebate totaling $2,500.

GM, which had a near record-high number of unsold vehicles at the end of June, was scheduled to announce its July U.S. sales results later Tuesday.

Like its cross-town rival Ford Motor Co. (F), GM has been struggling with an aging vehicle lineup, which requires more profit-eroding discounts to sell.