NASA will now pay $51 million for a single seat on Soyuz spacecraft.
NASA earlier said it planned to buy up to 24 seats aboard Russian Soyuz spacecraft to fly U.S. astronauts to the ISS after the space shuttle is retired in September 2010.
"We have reached an agreement with NASA to increase the price for a single seat on Soyuz space craft for U.S. astronauts traveling to the ISS to $51 million, with adjustment for inflation," said Alexei Krasnov, director of manned flight programs at Roscosmos.
In October 2005, Congress permitted the resumption of space deals with Roscosmos after amending the Iran Nonproliferation Act.
The act had banned such deals due to Russia's nuclear cooperation with Iran, which Washington accuses of pursuing a covert atomic weapons program. Iran says it needs the program to generate electricity.
In 2007, NASA signed a $719 million contract for 15 Soyuz seats on return trips to the ISS as well as for 5.6 tons of cargo. That came out to about $48 million per seat, or $144 million for a three seat flight.
NASA said in April "these services are being procured through Roscosmos because the Soyuz is the only proven crew transportation and rescue vehicle [other than the Space Shuttle which is scheduled for retirement in September 2010] currently compatible and able to dock to the ISS and capable of providing the needed services."