By Joey Roulette

WASHINGTON, April 9 (Reuters) - President Donald Trump's nominee to lead NASA, entrepreneur Jared Isaacman, will face questions from senators on Wednesday about on how to balance Trump's focus on reaching Mars with the U.S. space agency's flagship moon program.

Isaacman, CEO of payment processing company Shift4 Payments FOUR.N, is a close partner of Elon Musk's SpaceX who has flown to space twice as a private astronaut on the company's spacecraft.

The billionaire is in Washington for a confirmation hearing before the U.S. Senate Committee on Commerce, Science, & Transportation committee in which conflicting views on the moon and Mars as a destination for U.S. astronauts will be front and center.

If confirmed, Isaacman, 42, would oversee 18,000 employees and a budget of roughly $25 billion focused heavily on returning astronauts to the moon's surface, as part of a program called Artemis. Trump started the program during his first term.

But the president and Musk, who spent $250 million in support of Trump's presidential campaign and pushed for Isaacman's nomination, have become fixated on Mars as a national priority, raising questions about NASA's moon program for which billions of dollars have been committed.

Those views on the Red Planet could complicate Isaacman's path to confirmation, as he balances intense pressure from lawmakers and NASA to stay course with the moon program with pressure from Trump and Musk to get the U.S. to Mars.

"We will prioritize sending American astronauts to Mars," Isaacman will say in prepared testimony. "Along the way, we will inevitably have the capabilities to return to the moon and determine the scientific, economic, and national security benefits of maintaining a presence on the lunar surface."

The four astronauts assigned to NASA's Artemis 2 mission - which involves a flyby of the moon in 2026 before a subsequent moon landing mission - had front row seats in the hearing.

(Reporting by Joey Roulette; editing by Chris Sanders)

((Joey.Roulette@thomsonreuters.com; 7034696632;))