A SpaceX Falcon 9 rocket launch to the International Space Station was postponed on Monday, with officials citing problems with ground systems.
The SpaceX Dragon Crew-6 mission was scheduled to depart the Kennedy Space Center in Florida at 1:45 am (0645 GMT), carrying two NASA astronauts, a Russian cosmonaut and the second Emirati to voyage to space.
But just two minutes before lift-off, the launch was called off, or "scrubbed".
"Today's #Crew6 launch has been scrubbed due to an issue with ground systems," NASA posted on Twitter.
SpaceX said shortly after that it had begun unloading fuel from the rocket and the crew would disembark.
The launch will be rescheduled for a later date.
NASA's Stephen Bowen and Warren Hoburg, Russia's Andrey Fedyaev and Sultan al-Neyadi of the United Arab Emirates are to spend six months on the orbiting station.
Neyadi, 41, will be the fourth astronaut from an Arab country and the second from the oil-rich UAE to journey to space; his compatriot Hazzaa al-Mansoori flew an eight-day mission in 2019.
Neyadi described the upcoming mission as a "great honor."
Hoburg, the Endeavour pilot, and Fedyaev, the Russian mission specialist, will also be making their first space flights.
Fedyaev is the second Russian cosmonaut to fly to the ISS aboard a SpaceX rocket. NASA astronauts fly regularly to the station on Russian Soyuz craft.
Space has remained a rare venue of cooperation between Moscow and Washington since the Russian offensive in Ukraine placed the two in sharp opposition.
Such exchanges have continued despite those tensions.
Bowen, a veteran of three space shuttle missions, said politics rarely come up while in space.
"We're all professionals. We keep focused on the mission itself," the commander said. "It's always been a great relationship we've had with cosmonauts once we get to space."
While aboard the ISS, the Crew-6 members will conduct dozens of experiments including studying how materials burn in microgravity and researching heart, brain and cartilage functions.
The current crew is the sixth to be transported by a SpaceX rocket to the ISS. The Endeavour capsule has flown into space three times.
NASA pays SpaceX to ferry astronauts to the ISS roughly every six months.
The space agency expects Crew-6 to have a handover of several days with the four members of Crew-5, who have been on the ISS since October. Crew-5 will then return to Earth.
Also aboard the ISS are cosmonauts Dmitry Petelin and Sergei Prokopyev, as well as NASA astronaut Frank Rubio.
They had been scheduled to return home on March 28 but the cooling system of their Soyuz MS-22 capsule was damaged by a tiny meteoroid in December while docked with the ISS.
An uncrewed Russian Soyuz capsule, MS-23, took off on Friday from Kazakhstan to bring the three astronauts home. They are now scheduled to return to Earth in September.
Construction of the ISS began in 1998 at a time of increased US-Russia cooperation following the Cold War space race.
Russia has been using the aging but reliable Soyuz capsules to ferry astronauts into space since the 1960s.
But in recent years, Russia's space program has been beset by a litany of problems that have led to the loss of satellites and vehicles.