Ford Motor Co. could watch sales of its profitable F-Series pickup truck fall as much as 5% after crosstown rival General Motors Corp. launches its new pickup trucks later this year, according to an automotive analyst who downgraded his outlook for the Dearborn-based automaker on Thursday.

“We expect GM to take notable share from Ford in the full-size pickup segment in 2006 and, particularly, in 2007,” Himanshu Patel, an analyst for JP Morgan, wrote in a note to investors.