CHICAGO - Ford and Chrysler's sales rose modestly in US market in September, while General Motors' sales fell 11 percent in a month that had two fewer selling days than September 2012, according to figures released Tuesday.

General Motors said its September auto sales of 187,195 slid 11 percent year-on-year, while its retail sales fell 6 percent and fleet sales dropped by 27 percent.

GM's Buick and Cadillac brands posted sales increases for the month of 6.5 percent and 9.9 percent, respectively, while Chevrolet sales declined 14.7 percent and GMC sales fell by 9.7 percent.

Ford said its US September auto sales rose 5.8 percent. Fusion sedan sales jumped 62 percent in September while sales of the Fiesta subcompact rose 29 percent over the same month in 2012, setting a September sales record. Ford brand sales were up 6.3 percent for the month, while Lincoln brand sales dropped 5.1 percent.

Chrysler Group LLC said its September sales rose by 0.7 percent. The company sold 976 more vehicles compared with the same month a year ago.

Chrysler, Dodge and Ram Truck brands posted sales increases in September from the same month in 2012, while Fiat and Jeep brands both saw sales drop from September 2012.

US monthly auto sales have been posting year-on-year gains for more than two years, but analysts are projecting that trend will end with September's sales. Analysts are projecting a decline by as much as 4.4 percent, according to the Detroit News.

The main driver of the anticipated drop is two fewer selling days in September 2013 compared with the month in 2012. The big Labor Day sales weekend typically is included in September auto sales, but this year was included in August figures due to reporting on a sales month vs. calendar month basis.