Strong winds forced Austrian daredevil Felix Baumgartner to abort his attempt Tuesday at a record-breaking leap to Earth from the edge of space.
A new bid could be made later this week, a spokeswoman said, but everything depends on the weather, and the mission has only one spare balloon, after the first one was rendered unusable by the canceled launch.
The five-minute countdown had begun ticking down as the veteran sky diver prepared to hurl himself from a pressurized capsule 120,000 feet (37,000 meters) above sea level in the US state of New Mexico.
But as the clock reached zero, it became clear that conditions were too gusty to go ahead with the attempt.
The huge, gossamer-thin balloon which was to have taken Baumgartner aloft was buffeted mercilessly by the winds at the launch site in Roswell, New Mexico.
"Today's launch has been aborted... due to wind gusts making an attempt too risky," read a statement on the Red Bull Stratos mission's website.
Baumgartner looked visibly disappointed as he climbed out of the capsule, but said he was determined to go through with the mission.
"It's all about what we do now and accomplish now," he wrote in a message on the mission's Twitter feed.
"We've made it so far, there's no way turning back," he said.
The 43-year-old Austrian aims to break three records: the highest freefall from 23 miles (36 kilometers) above Earth; the fastest speed ever achieved by a human as he plunges through the sky; and the first person not in an aircraft to break the sound barrier of around around 690 miles (1,100 kilometers) per hour.
The jump was initially planned for Monday, but the attempt was delayed by 24 hours due to weather. Then the launch time began slipping again Tuesday morning, before the attempt was scuttled.
Baumgartner has been training for five years for the jump, during which he will be in freefall for some five minutes before opening a parachute at 5,000 feet (1,500 meters) to float back to the ground.
The biggest danger he faces is spinning out of control, which could exert G forces and make him lose consciousness. A controlled dive from the capsule is essential, putting him in a head-down position to increase speed.
Baumgartner has broken several records in the past, notably with spectacular base jumps from the Petronas Towers in Kuala Lumpur and the Christ the Redeemer statue in Rio de Janeiro, Brazil.
The mission, backed by a 100-strong team of experts, also hopes to contribute to medical and aeronautical research aimed at improving the safety of astronauts.
If and when it does go ahead, the ascent is expected to take between 2-3 hours. The descent, if all goes well, will take about 15 to 20 minutes -- five minutes or so in freefall, and 10 to 15 floating down with his parachute.
Spokeswoman Sarah Anderson said there would be no new attempt until Thursday at the earliest.
"Thursday could still be possible" for a new launch attempt, but a decision will not be taken until the day before then.
"Tomorrow (Wednesday) is definitely not an option," she said.
She added that any new attempt would have to use a different balloon.
"Today's balloon cannot be used... We have one back-up balloon on site. The weather team will not speculate more than two days, out because so much can change even in 12 hours."
Retired US Air Force Colonel Joseph Kittinger, who holds three of the records Baumgartner is trying to break, could be seen shaking his head, visibly upset in the mission control room Tuesday.
Kittinger, who jumped from 102,800 feet (31,000 kilometers) in 1960, said at the time that no one knew whether he could survive.
"We always like to push the envelope," said the 83-year-old, ahead of the aborted leap into the unknown.
