The Biden administration is seeking $24.8 billion for NASA in fiscal 2022, which would be a 6.6% increase from 2021, Nelson said during a press conference on Friday. But there's an amendment to the 2021 budget pending in Congress to boost moon landing budgets this year.

The amendment would allow NASA to offer a contract to a second company -- in addition to SpaceX -- to build a spacecraft that would land humans on the moon. Two companies tried to compete with SpaceX to provide the lander -- Washington-based Blue Origin owned by Amazon founder Jeff Bezos and Alabama-based Dynetics.

But a lack of funding from Congress prompted NASA to offer such a contract only to SpaceX, for $2.9 billion, on April 16.

SpaceX's bid was billions less than the other two firms proposed. Dynetics and Blue Origin have filed formal protests with the government's watchdog for such bids, the Government Accountability Office.

"They [some members of Congress] want competition, and so do I," Nelson said in a phone interview Thursday. "I suspect that with this human landing system, that we're going to see more money forthcoming from the Congress in order to have a vigorous competition."

Sen. Maria Cantwell, D-Wash., proposed the additional $10 billion, but Sen. Bernie Sanders, I-Vt., has formally opposed it with his own amendment reading only: "To eliminate the multibillion-dollar Bezos Bailout."

"Competition is always good because at the end of the day, with competition you get the best price, and you get the greatest efficiency," Nelson said.

However, Nelson said he doesn't support the same kind of competition for the rocket that will launch humans from Earth to the moon again -- the SLS.

The massive 212-foot core stage of the rocket was delivered to Kennedy Space Center in Florida on April 29, following the expenditure of $17 billion to build it.

Nelson said he considers the construction of SLS by Boeing to be safer than options under development by SpaceX, Blue Origin and other companies due to intense NASA oversight of the process.

During lunar landing missions, SLS would deliver astronauts to lunar orbit and SpaceX's Starship -- or possibly additional spacecraft if approved -- would rendezvous with SLS and take astronauts to the moon's surface.

NASA's plan is for SLS to launch on an uncrewed test flight to the moon by the end of 2021.

"We're going to know shortly" if the SLS is a proven human-rated vehicle, Nelson said.

Asked if he would support the replacement of SLS by a privately built, more efficient moon rocket in the future, Nelson said, "I don't know, I haven't seen one."

SpaceX has flown several test flights of its Starship moon and Mars rocket in Texas. The company intends to fly Starship to the moon as part of the human lander contract, but Starship -- like SLS -- has yet to reach space.

Under the administration of President Joe Biden, NASA will also have a stronger focus on climate change, Nelson said.

During a press conference about the 2022 budget on Friday, Nelson said Biden's budget request contains record-high levels of funding for science, and funding to develop regular astronaut missions to the moon.

"This is a very aggressive forward-leaning budget for NASA," Nelson said on Friday. "The Biden Administration is proving that science is back. The record funding, and the science area, will help NASA address the climate crisis and advance robotic missions that will pave the way for astronauts to explore the moon and Mars."

The agency announced Wednesday it would launch five new Earth observation satellites over the next decade with sophisticated technology to track changes driven by climate change.

"It is going to be significantly more advanced, and it is going to create a 3D picture of all the intricate systems ... oceans, land, the atmosphere and ice, and how all of that interrelates," Nelson said.