Isaacman, 42, a billionaire entrepreneur and private astronaut who is a close associate of Elon Musk, appeared during a rare second confirmation hearing that followed Trump's re-nomination of him in November for the top post at the US space agency.

Isaacman told senators that, if confirmed for the job, he would ensure the success of the Artemis lunar exploration program started in 2017, during Trump's first administration.

"America will return to the Moon before our great rival, and we will establish an enduring presence to understand and realize the scientific, economic and national security value on the lunar surface," Isaacman said.

His nomination -- first announced after Trump won the 2024 election, then withdrawn in April 2025 and again reissued last month -- reflects the president's on-again, off-again relationship with Musk, the world's richest man and founder of SpaceX, among other ventures.

"I have to say for a moment, (this) feels a bit like Groundhog Day," Republican Senator Ted Cruz, chairman of the Senate Committee on Commerce, Science, and Transportation, said as he opened the hearing.

Trump's decision to withdraw Isaacman's first nomination took place as the president feuded in the spring with Musk, who had headed Trump's so-called Department of Government Efficiency (DOGE).

But Trump and Musk appear to have since reconciled.

- Second space race -

It has been 53 years since humans last landed on the surface of the Moon. In a Cold War space race with the Soviet Union, the US last completed that feat with its Apollo 17 mission in December 1972.

During his first confirmation hearing in April, Isaacman stated that he wanted to prioritize sending astronauts to Mars. But on Wednesday, he spoke more cautiously about Mars and more strongly emphasized the goal of returning a manned US mission to the Moon as soon as possible.

NASA's Artemis program to return to the Moon, however, has faced numerous delays in recent years.

Experts warned in September that the lunar lander developed by Musk's SpaceX might not be ready in time.

Such a complication would put the United States at risk of being overtaken by China, which also aims to reach the Moon by 2030, Trump's appointee indicated at Wednesday's hearing.

"I think it's imperative that we do so, and failing to do so calls into question American exceptionalism beyond just our expertise in the high ground of space," Isaacman said.

While the Trump administration was open several months ago to revising the Artemis program in favor of Mars, this prospect now seems to be fading.

Since the rift between the US president and billionaire Elon Musk, who is obsessed with the red planet, US authorities have been emphasizing their determination to outpace Beijing in what they call the "second space race."

If confirmed to head NASA, Isaacman would need to ensure that SpaceX delivers the lunar lander on time.

Isaacman made his fortune in online payments as the founder and CEO of Shift4. He has flown two private space missions aboard Musk's SpaceX rockets and has been a key customer and advocate for the company's space exploration goals.

Asked about a potential conflict of interest with Musk, with whom he is reportedly very close, Isaacman assured that he maintains only professional relations with him.

"Senators, I'm not here for a personal gain to favor or enrich contractors," Isaacman said.