The franchise for Central Trains, which operates rail services in the Midlands, West Country and south Wales, has been extended until November 2007.
The announcement by the Department for Transport means the firm will run the services until new rail franchises come into force.
The extension will allow for all four rail franchises in the region to end at the same time.
Timetables and the level of service will be maintained, the firm said.
Three new franchises in the East Midlands, West Midlands and Cross Country will replace the current four franchises operated by Central Trains, Silverlink, Virgin Cross Country and Midland Mainline.
The successful bidders for the new franchises are expected to be announced by summer 2007.