DETROIT - General Motors Co GM.UL could extend its offer of a 60-day, money-back guarantee for consumers when the marketing program expires at the end of November, GM Vice Chairman Bob Lutz said on CNBC on Friday

It's possibly renewable. We'll see what kind of experience we have, Lutz said in an interview.

Lutz said that GM expects way under 1 percent, of consumers who buy new Cadillacs, Chevrolets, GMC or Buick vehicles will return them in the guarantee program.

Two weeks ago GM launched an aggressive marketing program that centers on stepped-up advertising and the money-back guarantee.

The campaign is an attempt to convince reluctant American consumers that GM's products are competitive with the best vehicles from import brands like Toyota that have eaten into the automaker's once-dominant U.S. market position.

In the past year, Toyota Motor Corp overtook GM as the world's top vehicle-seller, and Detroit-based GM underwent a 40-day stay in bankruptcy and emerged owned 61-percent by the U.S. Treasury.

Lutz said GM was pleased with the initial results of the guarantee program.

He said research by GM and outside analysts showed it had increased the pool of consumers who say they would consider buying a GM vehicle even though it had not boosted sales yet.

Industry-wide auto sales for September are expected to be near lows for the year after sales boomed in August on the U.S. government's Cash for Clunkers incentive program.

We never did want to look at this program as immediately driving sales, Lutz said.

GM Chief Executive Fritz Henderson on Thursday said GM expected September total U.S. auto sales to drop to near 9 million vehicles on an annualized basis. The previous low for 2009 was February's sales rate of 9.2 million vehicles.

GM expects 2009 to end at around 10 million to 10.5 million in total sales with 2010 sales recovering to near 13 million.

In 2008, U.S. total sales were 13.2 million. This year will market the fourth consecutive one of falling U.S. sales.

Lutz said GM dealers are low on inventory of better-selling vehicles but have plenty of inventory of full-sized sports utility vehicles and pickup trucks. (Reporting by Bernie Woodall and Kevin Krolicki, editing by Dave Zimmerman)