WASHINGTON, May 22 (Reuters) - NASA and Boeing ( BA ) are

targeting June 1 for the company's first crewed launch of its

Starliner spacecraft as engineers investigate the cause of a

helium leak and examine how it could affect crucial parts of the

mission, the agency said Wednesday.

The helium leak on Starliner's propulsion system has held up

the spacecraft's first mission to space carrying humans,

initially planned for May 7 but successively delayed as NASA and

Boeing ( BA ) attempt to fix the issue and run new tests on the

spacecraft.

The U.S. space agency said engineers have broadened their

review into the leak, which was traced to a valve component on

a single thruster, to include an assessment of Starliner's

propulsion system and how it might be impacted by the

spacecraft's helium system.

Starliner's helium system is used to add pressure to the

fuel that powers its onboard thrusters, which are used to

maneuver the spacecraft in orbit.

Boeing's ( BA ) Starliner spacecraft, developed to ferry NASA

astronauts to the International Space Station (ISS), has been

delayed years and is more than $1.5 billion over budget.

Persistent Starliner development challenges have illustrated

Boeing's ( BA ) struggle to compete with Elon Musk's SpaceX on tighter

budgets.

Starliner's debut crewed flight includes NASA astronauts

Suni Williams and Butch Wilmore. The mission is a final test

before NASA can certify Starliner for routine missions to and

from the ISS.

The space agency said Boeing ( BA ) has additional launch

opportunities on June 2, 5 and 6 should it miss the June 1

window.