September proved to be a tough month for Ford Motor Company (NYSE: F) with the American auto maker posting a 21 percent decline in U.S. sales. While Ford took a steep hit to U.S. sales, its American counterpart General Motors Corporation (NYSE: GM) was able to perform better, showing flat sales growth for the month.

While the large drop is a tough pill to swallow, Ford states that it is in line with the company's expectations that it set out at the start of the year. The auto maker has been making a conscious effort to cut back on its sales to rental business's and it blames September's weakness mostly on this fact. All year the company has been reducing the sales volume to be used in rentals in an attempt to curtail the negative impacts this business segment can post to brand image and profits. The company had a 62 percent decline in sales to rental car fleets.

While the company's planned reduction in sales to rental car fleets can be explained away, what the company had not been counting on was a decline of 21 percent in sales of its popular F-150 pickup line. The company has been losing out in the truck market to newer pickups from GM and Toyota Motor Corporation (NYSE: TM).

Taking into account the weak September figures, Ford now has a total drop of 13 percent in sales through the first nine months of the year. The last time the company had a month where sales rose was all the way back in October 2006