The Starliner and its crew will return no earlier than August 18, Stich told a press conference at Kennedy Space Center in Florida on Friday.
The window for the return flight would extend into early September, Stich added.
NASA's planned schedule for crewed flights to and from the ISS over the next two months was first to "bring Butch and Suni home on Starliner, [then] launch Crew 9 [to the ISS] and then bring Crew 8 home," he said.
Starliner was launched with its two-astronaut crew on June 5 but five of its 28 thrusters failed at different times during its flight to the ISS and five helium leaks were also recorded.
The spacecraft's return flight was originally scheduled for June 14 but has been repeatedly delayed since then while engineers back on Earth tried to solve the problems, NASA officials have acknowledged.