Chrysler Group LLC's U.S. sales fell 15 percent to 93,222 units in August due to inventory shortages related to extensive summer shutdowns during its bankruptcy restructuring, a source briefed on the matter said on Tuesday.

Chrysler's August sales did mark a 5 percent increase from July, when it sold 88,900 units, the source told Reuters, asking not to be named because the information has not been made public.

The No. 3 U.S. automaker's inventory was reduced to 28 days of supply by the end of August, the source said.

To boost sales in September, Chrysler will be offering $4,500 of consumer cash or zero-percent financing for up to six years on select 2009 model-year vehicles, the source said.

On some 2010 model-year vehicles, Chrysler will be offering consumer cash of $2,000, the source added.

(Reporting by Soyoung Kim, editing by Gerald E. McCormick)

Chrysler Down