Vice President Pence on Tuesday called for American astronauts to return to the lunar surface within five years, a bold and exceedingly difficult challenge that would push NASA to its limits.

In a fiery speech in Huntsville, Ala., Pence repeatedly said the space agency needs to act with a renewed sense of urgency to land humans on the moon for the first time since 1972. And he cast the mission as part of a new space race against superpowers such as Russia and China, which landed a spacecraft on the far side of the moon earlier this year.

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But most of all, Pence said NASA and its major programs have been stifled by a crippling bureaucracy that prevented the agency from moving more boldly in human exploration.

“It's not just competition against our adversaries,” Pence said. “We're also racing against our worst enemy: complacency.”

Pence did not provide details on how the agency would achieve landing humans on the moon in the five-year time frame, a monumental goal NASA had been hoping to achieve by 2028. He provided no details on the cost or how the mission would unfold. He added that he had learned the details of NASA’s plans only five minutes before stepping onstage.

NASA did not immediately respond to a request for more details about the plan or how it would be funded.

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In his speech, which came during the fifth meeting of the National Space Council, Pence took a shot at the rocket NASA is developing, known as the Space Launch System. With Boeing as the prime contractor, the rocket is years behind schedule and billions of dollars over budget.

Recently, NASA Administrator Jim Bridenstine told a Senate hearing that its first flight was going to be once again delayed, and, as a result, the agency would look at sidelining it in favor of commercial rockets.

Companies such as SpaceX, the United Launch Alliance and Blue Origin are all developing new rockets that, while not as capable as the SLS is designed to be, would be less expensive. (Jeffrey P. Bezos, who owns The Washington Post, founded Blue Origin.)

Pence doubled down on the idea of bypassing the SLS Tuesday, lamenting how the program has “been plagued by bureaucratic inertia, by what some call the paralysis of analysis.” He said he was saddened to hear that the first flight of the rocket would be pushed to 2021.

“Now that would be 18 years after the SLS program was started and 11 years after the president of the United States directed NASA to return American astronauts to the moon,” Pence said. “Ladies and gentlemen, that’s just not good enough.”

He also took aim at NASA’s bureaucracy, saying the agency “must transform itself into a leaner, more accountable and more agile organization. If NASA’s not currently capable of landing American astronauts on the moon in five years, we need to change the organization, not the mission.”

In the space community, the announcement was greeted warmly for challenging the status quo and pushing NASA to move faster.

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“It was a sense of urgency that enabled the Apollo missions to successfully land on the Moon the first time,” said Ellen Stofan, the former chief scientist at NASA who now runs the National Air and Space Museum. “This same urgency is what it will take to accomplish a successful mission to the Moon in the future -- and this call for a specific landing date has that sense of purpose and urgency.”

Philip Metzger, a planetary scientist at the University of Central Florida, also applauded the fast timeline, but said that “five years is very challenging. I’m not sure it can be done. But it’s a good goal.”

Pence’s speech comes at a time of increased activity and competition in space. The White House has pushed the creation of a Space Force to help the military combat potential adversaries in orbit. Earlier this year, China landed an uncrewed spacecraft on the far side of the moon and plans to return another spacecraft later this year. India and Israel also plan to land spacecraft on the moon this year.

The White House, however, has been looking to make a big splash in space, hoping to send an Orion spacecraft without crew in a trip around the moon in this presidential term. The administration’s plan calls for landing of humans on the moon in a second term, should President Trump be reelected.

In a statement, the Coalition for Deep Space exploration, a consortium of aerospace companies, said that while it supports "aggressive timelines and goals, we also are cognizant of the resources that will be required to meet these objectives. Bold plans must be matched by bold resources made available in a consistent manner in order to assure successful execution.”

It’s not clear, though, how NASA intends to pull off a human landing in five years. Its current plan is to build what’s called a Gateway, an outpost that would orbit around the moon. It’s also unclear what rocket the agency would use. The SLS has been under fire for its delays and cost overruns. And Pence indicated the agency would look at alternatives, if need be.

“If commercial rockets are the only way to get American astronauts to the moon in the next five years, then commercial rockets will be,” Pence said. “ ‘Urgency’ must be our watchword. Failure to achieve our goal to return an American astronaut to the moon in the next five years is not an option.”

Bridenstine said he believed that Boeing and the other contractors, working alongside NASA, could accelerate the schedule so that SLS could be launched in 2020. And he said the agency was dedicated to meeting the White House’s goal.

“Our agency is going to do everything in its power to meet that vision, to meet that deadline,” Bridenstine said. “We got it loud and clear.”