General Motors Corp. will start a new incentive program that offers at least $1,000 off most vehicles in its lineup, including some ’08 models, sources say.

Called “Time to Buy,” the new scheme takes effect tomorrow and comes despite GM’s efforts to distance itself from incentives, which in addition to cutting into vehicle profits can badly diminish brand equity.

Sources say the new program will run through Oct. 1, and selected vehicles will receive spiffs of up to $2,000. The auto maker also will make 0% financing available on select models. The program puts particular focus on full size SUVs and the subcompact Chevrolet Aveo, sources say. Calls to GM were not returned.

The fresh incentives also arrive as U.S. auto makers are poised to gain market share in September for the second straight month, according to Ward’s forecast. It would mark the first back-to-back gains for GM, Ford Motor Co. and Chrysler LLC since the August-October 2006 timeframe.

GM is expected to lead the Detroit Three in September by posting a 6.8% sales gain over year-ago.