The Soyuz landed nearly 500 kilometres (310 miles) off target in the Kazakh steppe Sunday, and rescue services could not find US astronauts Kenneth Bowersox and Donald Pettit and Russian cosmonaut Nikolai Budarin for more than two hours.

After a nail-biting wait at Russian mission control outside Moscow, during which O'Keefe and the astronauts' families did not even know if they were alive or not, a rescue plane spotted the three crew members outside their capsule.

"If I said that I was worried that would be a real understatement of how I felt. At one moment I said to myself: 'Oh God!, I can't believe it can happen twice in a row'," O'Keefe told the Russian daily Izvestia.

Columbia disintegrated during re-entry to the Earth's atmosphere on February 1, killing all seven crew members and leading NASA to suspend all shuttle missions, including those to the International Space Station.

Russian spacecraft now provide the only transportation to the space station and Sunday's flight back from the ISS was the first return from space since the Columbia tragedy.

"You should have seen how courageously the wives of the astronauts behaved during those hours," said O'Keefe in comments translated into Russian.

Bowersox at a press conference Tuesday recalled the tears they saw in the eyes of their wives when they met up again.

The spouses had been "especially worried after what happend with Columbia," he said.

The US-Russian trio made a much steeper than expected uncontrolled entry for their landing on the plains of Kazakhstan after an apparent malfunction onboard.

The astronauts Tuesday denied precipitating their off-target landing by pressing the wrong button as it emerged their Soyuz TMA-1 craft -- a new, modified spaceship -- may accidentally have gone into reverse docking mode.

The daily Russia Journal quoted a cosmonaut, Talgat Musabayev, as saying that Russian space experts believe the problem was caused by software in the guidance computer that was installed in the Soyuz.

SPACE.WIRE