CAPE CANAVERAL (CBSMiami/AP) — The countdown to the historic launch of the SpaceX Dragon capsule is drawing closer.

If weather cooperates, the first manned mission for NASA on U.S. soil since the space shuttle will lift off Wednesday afternoon at 4:33 p.m. from Cape Canaveral.

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Wednesday will also mark the first-ever crewed mission for SpaceX in its 18-year history and the first time NASA astronauts have blasted off on a private spacecraft.

The SpaceX Dragon capsule is being launched by a Falcon 9 rocket, owned by tech billionaire Elon Musk.

The SpaceX Falcon 9 rocket with the Crew Dragon spacecraft attached is prepared for liftoff from launch pad 39A at the Kennedy Space Center in Cape Canaveral. (Photo by Joe Raedle/Getty Images)

NASA is keeping a close eye on the ever changing Florida weather.

“Everything is looking good, we are, as of right now, we are go for launch. The weather is about 60 percent favorable for launch tomorrow, which is good news compared to where we were yesterday, we were at 40 percent, so the trend is in the right direction and um, we are very, very excited,” said NASA Administrator Jim Bridenstine.

If the launch is delayed due to weather, NASA says there are backup opportunities on Saturday and Sunday afternoon.

NASA is asking people not to visit the area to watch the launch in person due to the coronavirus pandemic.

“This room is empty, we would love to have this room full. We would love to have it filled with reporters, we’d love to have it filled with space enthusiasts, and unfortunately we are in the middle of the coronavirus pandemic. Our country has been through a lot, but this is a unique moment where all of America can take a moment and look at our country do something stunning again, and that is launch American astronauts on American rockets from American soil.”

This mission is just a test flight to the International Space Station but NASA says it eventually could certify SpaceX for astronaut missions to the ISS.

Veteran NASA astronauts Doug Hurley and Bob Behnken spent three weeks in quarantine to protect them against COVID-19 leading up to the launch.

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President Donald Trump and Vice President Mike Pence plan on attending the historic launch, which is part of NASA’s longer term strategy back to the moon and then on to Mars.

Bridenstine says both the space agency and SpaceX have been diligent about making sure everyone in the launch loop knows they’re free to halt the countdown if there’s a concern. He says “our highest priority” will remain the astronauts’ safety.

Bridenstine said he texted the two astronauts Monday and told them, “`If you want me to stop this thing for any reason, say so. I will stop it in a heartbeat if you want me to.’ They both came back and they said, ‘We’re go for launch.’”

SpaceX has been launching cargo capsules to the space station since 2012.

It is on a streak of 62 successful launches and Crew Dragon is armed with escape system. If the rocket falters, its engines can push the capsule away, landing the crew safely in the ocean.

NASA will have input throughout the countdown, but in the end, it will be SpaceX giving the final go — with NASA’s concurrence.

“SpaceX is controlling the vehicle, there’s no fluff about that,” Norm Knight, a NASA flight operations manager, said Monday.

While the odds of acceptable launch weather improved Tuesday to 60%, that didn’t factor in conditions along the Dragon’s route to orbit.

SpaceX needs relatively calm waves and wind up the U.S. and Canadian seaboard and across the North Atlantic to Ireland, in case astronauts Hurley and Behnken need to make an emergency splashdown.

The last time astronauts launched from Florida was on NASA’s final space shuttle flight in July 2011. Hurley was the pilot of that mission.

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(© Copyright 2020 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)