Safety history: This is the first major issue with a Russian Soyuz booster since a mission was aborted on-pad in August 1983, when a capsule pulled away from an exploding booster. "Today showed again what an incredible vehicle the Soyuz is, to be able to save the crew from such a failure". It was not clear why the two stages had collided, Krikalev said, saying it was possible the rocket had changed trajectory slightly.
The incident comes as the US has been making progress in its quest to end Russia's monopoly on manned flights to the ISS by encouraging private companies to conduct launches.
Russian officials said all manned space flight missions would be suspended until investigators figure out what went wrong. A state commission has been established to investigate the incident.
Search and rescue teams were scrambled to the touchdown location as NASA revealed the descent meant the Russian-built Soyuz MS-10 spacecraft had to take "a sharper angle of landing compared to normal".
This morning's mishap is the fourth time in history the Soyuz space program has had to conduct a ballistic reentry into Earth's atmosphere.
It was to be the first space mission for Hague, who joined NASA's astronaut corps in 2013.
But the delay represents no danger to them, experts have said.
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In 2008, Expedition 16 crew experienced a similar steep ballistic descent on return from the ISS as did cosmonauts returning from the Salyut space station in 1979.
The ISS crew was getting regular updates on the mission, as you'd expect, and learned about the rocket failure just shortly after it happened.
The incident began with a booster emergency light illuminating in the ship of NASA astronaut Nick Hague and Roscosmos astronaut Alexei Ovchinin. Write to us in the Comments section, and visit our Facebook page.
"The guys will definitely fly".
"Rescue services have been working since the first second of the accident", Rogozin wrote on Twitter.
Unmanned cargo launches carry food and other supplies to the ISS and use the same rocket system as the Soyuz. But the Russian space agency also considered the possibility of sabotage. Roscosmos sent more than 70 rocket engines back to production lines to replace faulty components, a move that resulted in a yearlong break in Proton launches and badly dented Russia's niche in the global market for commercial satellite launches.
A Progress rocket was lost in the atmosphere in December 2016. Rogozin accused Musk on state television last week of selling seats on SpaceX at below cost to undermine Russia's market share.
Russia's TASS news agency said the capsule carrying the two men separated from the troubled rocket safely.