By Marisa Taylor and Nandita Bose

WASHINGTON (Reuters) -The role of Elon Musk's SpaceX in an ambitious new U.S. missile defense system is in question following the dramatic feud last week between the billionaire entrepreneur and President Donald Trump, according to three people familiar with the project.

The White House until recently had considered a plan for SpaceX, Musk's rocket and satellite venture, to partner with software maker Palantir and drone builder Anduril to construct crucial elements of the project, dubbed "Golden Dome." The administration had instructed the Pentagon to prioritize a network of satellites for the purpose, these people said.

But a new framework for the system, which would seek to track and prevent possible missile attacks against the United States, is now being considered that could reduce the role of SpaceX. One possibility, the three people said, could initially forego SpaceX's satellite capabilities and focus on the expansion of existing ground systems for missile defense instead.

In a statement, a White House spokesman said "the Trump Administration is committed to a rigorous review process for all bids and contracts." A senior Defense Department official said the Pentagon "has no announcements regarding future contracts associated with the Golden Dome effort."

SpaceX, Anduril and Palantir didn't respond to requests for comment.

A reduced role for SpaceX would represent the first known setback to Musk's huge volume of business with the U.S. government since his break with Trump last week. The shift in plans, especially for a project that Trump has touted as paramount for U.S. defense strategy, also underscores the highly personalized nature of the president's leadership, aerospace and defense experts said.

"That people guiding the program or building it are approved based on their political affiliation signals a real concern that the project itself is very politicized and not being conducted on the technical merits," said Laura Grego, a missile defense expert and research director at the Union of Concerned Scientists, a non-profit based in Cambridge, Massachusetts.

In its statement to Reuters, the White House said any decision would be made "prioritizing the best deal for America and leveraging the most advanced and innovative technology."

Trump in May said the defense shield should be operational by the end of his presidency, January 2029. But industry experts have said that timeframe, and a projected cost of some $175 billion, could be too optimistic.

The change in the proposed "architecture" of the system, the three people said, could have the political advantage of allowing the current administration to deliver at least a portion of it. It isn't clear how soon a final decision on the project could come or whether the ultimate role of any company, including SpaceX, has been determined.

Trump's efforts to roll out the project fast have led to uncertainty about the project's details and a scramble by contractors to be involved, industry experts and some of those involved in its development told Reuters. "To this day, no one knows what the requirements are," said one of the people familiar with the process. "There isn't a coordinated effort with a true vision. All of these companies are just grabbing at this pot of money."

SpaceX, Anduril and Palantir were all founded by entrepreneurs who have been major political supporters of Trump. The three companies had previously met with top administration officials and decisionmakers from the Defense Department to discuss Golden Dome, according to people familiar with those discussions.

Before his high-profile falling out with the president, Musk served as a key Trump advisor and donated more than a quarter of a billion dollars to help elect him. But the recent dispute, which included Musk calling for Trump's impeachment and accusing the president of improper involvement with disgraced financier and sex offender Jeffrey Epstein, triggered the change in direction, the three people told Reuters.

"Because of the blowup, the Pentagon has been given the space to look at other alternatives," one of the people said.

In recent days, Musk has sought to temper the dispute, saying he regretted some of his comments and taking down some of his social media criticism of Trump, including the call for impeachment. Earlier this week, Press Secretary Karoline Leavitt told reporters that Trump appreciated Musk's apology and that she was unaware of any administration efforts to review Musk contracts because of the dispute.

Reuters couldn't determine whether Musk's conciliatory overtures might improve SpaceX's chances of winning Golden Dome contracts or securing further new business with the U.S. government.

SpaceX had pitched for a part of the Golden Dome initiative called the "custody layer," a constellation of between 400 and 1,000 satellites that would detect missiles, track their trajectory, and determine if they are heading toward the U.S., Reuters reported in April. In a January 27 executive order, Trump mandated the selection of a proposed "architecture" for Golden Dome and an implementation plan by the end of March.

The order called a missile attack "the most catastrophic threat facing the United States."

(Additional reporting by Mike Stone and Idrees Ali. Editing by Chris Sanders and Paulo Prada.)