WASHINGTON (Reuters) -Elon Musk's SpaceX and United Launch Alliance are expected to each win a U.S. Space Force rocket launch contract on Friday worth billions of dollars over the next several years to send some of the Pentagon's most sensitive satellites into space, according to two people familiar with the procurement decision.

The Space Force's flagship National Security Space Launch procurement program, which is poised to assign roughly 50 missions through 2029 in incremental task orders, is expected to announce its selection decision on Friday, with SpaceX and ULA among the winners, the sources said.

Space Force's Space Systems Command office did not immediately respond to a request for comment.

The awards are part of the Phase 3 program's "Lane 2" track. That track contains the Pentagon's most difficult and expensive missions, involving a variety of complex orbits around Earth, for which only the top U.S. launch companies with the most experience are to compete.

SpaceX, with its Falcon 9 rocket, is the world's most active launch company. It has launched dozens of military space missions in recent years.

Its CEO, Musk, a special government employee and close ally of President Donald Trump, has wielded enormous influence over the U.S. government, from slashing federal agencies in his government efficiency effort to pushing allies to lead federal agencies that oversee billions of dollars' worth of SpaceX government contracts.

Friday's awards have been years in the making. It is a third phase of a program governing how the U.S. Defense Department purchases rides to space for its military and intelligence satellites, a lucrative area of government procurement once dominated by the Boeing ( BA ) and Lockheed Martin ( LMT ) joint venture, United Launch Alliance.

But SpaceX's rise in the past decade as a dominant launch player with its reusable Falcon 9 rockets - offering a cost-cutting capability its rivals have been slower to match - has made it a key vendor for the Pentagon, which is also increasingly reliant on the company for satellite-based military intelligence.