Alexei Krasnov, in charge of manned flights at Roscosmos, said the decision was made by participants at the International Astronautical Congress in Naples, Italy, this week.

The two-person expedition - with crew members from Roscosmos and NASA - will be a first test, the result of which will determine whether all flights are extended to a year, he said.

"The fundamental decision has been made, only the formalities remain to be negotiated. So far, we are talking about a single mission," Krasnov told RIA news agency.

"If it proves effective, we will be able to discuss with partner countries a permanent transition from half-year flights to year-long flights."

Veteran Russian cosmonaut Yuri Malenchenko, NASA astronaut Sunita Williams and Japanese astronaut Akihiko Hoshide are currently in orbit aboard the International Space Station.

They are to be joined by another trio - Kevin Ford, Oleg Novitsky and Yevgeny Tarelkin - due to blast off from the Baikonur cosmodrome in Kazakhstan at the end of the month, their flight delayed by a week due to a technical equipment glitch.

Russia's space programme has suffered a series of humiliating set-backs in recent months that industry veterans blame on a decade of crimped budgets and a brain drain.

While none of the mishaps have threatened crews, they have raised questions over Russia's reliability, cost billions in losses and dashed Moscow's dreams of ending a more than two-decade absence from deep space exploration.

Since the retirement of the U.S. space shuttles last year, the United States is dependent on Russia to fly astronauts at a cost of $60 million per person.

(Reporting By Nastassia Astrasheuskaya, editing by Rosalind Russell)

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