A vehicle propulsion system includes an engine and a first electric machine each configured to selectively provide torque to propel the vehicle. A second electric machine is coupled to the engine to provide torque to start the engine from an inactive state. A high-voltage power source is configured to power both of the first electric machine and the second electric machine over a high-voltage bus. A propulsion controller is programmed to start the engine using cranking torque output from the second electric machine powered by the high-voltage power source. The controller is also programmed to operate both of the first electric machine and the combustion engine to propel the vehicle in response to an acceleration demand greater than a threshold. The controller is further programmed to decouple the engine and propel the vehicle using the first electric machine in response to vehicle speed less than a speed threshold.