DETROIT (Reuters) - General Motors Co (>> General Motors Company) will add a third shift and 750 jobs at its Missouri assembly plant to build more of its new mid-sized pickup trucks, the No. 1 U.S. automaker said on Tuesday.

With early orders for the Chevrolet Colorado and GMC Canyon at nearly 30,000, GM decided to add the third shift at the Wentzville plant to meet expected demand. The additional shift at the plant, which also builds full-size vans, is expected to start in early 2015.

GM counts on its full-size pickups, the Chevy Silverado and GMC Sierra, for the bulk of its profits, but is aiming to boost its share of the overall truck market with the smaller companions that it feels will appeal to a different group of buyers. Rivals Ford Motor Co (>> Ford Motor Company) and Chrysler Group (>> Fiat SpA) do not sell mid-sized pickups in the U.S. market.

Production of the 2015-model Colorado and Canyon trucks is already under way and shipping to dealers will begin soon, a spokesman said. The trucks will go on sale in October.

GM has not provided sales forecasts for the new trucks other than saying the Colorado will be more successful than its last appearance when U.S. sales peaked in 2005 above 128,000 vehicles.

The 750 new jobs at the GM plant are in addition to the 1,315 jobs committed to with the launch of the smaller pickups and the addition of a third stamping press, investments worth $513 million. The plant currently employs some 2,600 people, and that will rise to about 3,350 at full capacity, the spokesman said.

(Reporting by Ben Klayman in Detroit; Editing by Meredith Mazzilli)

Stocks treated in this article : Ford Motor Company, Fiat SpA, General Motors Company