Three astronauts set to travel to the International Space Station this month Wednesday voiced faith in Russia's space programme despite a delay to their trip caused by the failed launch of a cargo ship.

Russian Oleg Kononenko, NASA astronaut Kjell Lindgren and Kimiya Yui of Japan -- fans of the "Star Wars" saga who had posed in Jedi robes ahead of their mission -- said they stood by Russia's space engineers and the veteran Soyuz rocket that will take them aloft.

Lindgren, 42, who will be making his first space voyage, admitted he and his colleagues were "disappointed" their launch had to be delayed from May but said they all trusted the Russian spacecraft.

Russia put all space travel on hold while it probed the loss of an unmanned Progress freighter taking cargo to the ISS in late April. The doomed ship lost contact with Earth and burned up in the atmosphere.

"We are confident in the engineers, the professionalism of the Russian space programme, to identify the problems and to ensure that that problem does not exist with our spaceship," Lindgren told reporters ahead of the astronauts' departure scheduled for July 23.

The glitch, which Russia has blamed on a problem in a Soyuz rocket, also forced a group of astronauts to spend an extra month aboard the ISS.

A workhorse of space that dates back to the Cold War, the Soyuz is used for manned and unmanned flights, which explains why the crew's launch was postponed while investigations were carried out.

"The delay has given us additional time for some refresher training, to spend time with our families and to rest," Lindgren said in the Star City space base, nestled in a forest outside Moscow.

"And I think that we are ready to fly whenever the spacecraft is ready to take us to space," he said, speaking at the Soviet-era Yury Gagarin Cosmonauts' Training Centre decorated with old mosaics.

The crew's Russian commander Kononenko, 51, was equally at ease.

"I think we trust the spacecraft we will fly in," he said, while conceding that, in space, everything might not go as planned.

"Unexpected things can happen."

"Machinery is machinery. It can let you down. But we trust the people, the engineers who created this machinery."

"There is rescue equipment for the crew," he added.

Kononenko said that none of the men were afraid.

"We aren't feeling some kind of visceral fear. There isn't any fear or worries."

The Japan Aerospace Exploration Agency's Yui, who like Lindgren is making his maiden space voyage, also stressed that the delay had given them more time to prepare for the mission.

"Right now we are very, very ready," he said with a smile. "I know that the Soyuz is a very reliable, safe ship," the 45-year-old said in Russian.

"I believe that our launch will be the safest launch ever."

- R2-D2 mascot-

The trio said they were Star Wars fans and had chosen the R2-D2 robot, a key character in the film series, as the mascot for their expedition.

"I was talking with my kids and we decided that we should have an R2-D2 in our spaceship as well," said Lindgren, who has three children and describes himself on Twitter as a "space nerd in paradise."

For the official poster of the ISS Expedition 45, the astronauts posed wearing brown Jedi robes and clutching light sabres.

The trio will be joining Russia's Gennady Padalka and Mikhail Kornienko, as well as Scott Kelly of NASA, who are continuing research and maintenance aboard the ISS.

They will conduct a number of scientific experiments including controlling robots remotely.

Kononenko said that at the request of young space enthusiasts, he would also study the behaviour of soap bubbles, among other experiments, while Yui promised to tweet often.

The proliferation of online social networks has propelled many astronauts to fame, including Italy's Samantha Cristoforetti who returned from the ISS last month to find she had more than half a million followers on Twitter.