The NASA space agency says it has signed a contract extension with its Russian counterpart regarding crew transports to the International Space Station.

The U.S. agency said in an online statement the $306 million deal with Russia's Federal Space Agency Roscosmos will involve four launches by the Roscosmos Soyuz program, RIA Novosti reported Friday.

NASA said on its Web site Thursday the new deal includes "comprehensive Soyuz support, including all necessary training and preparation for launch, crew rescue, and landing of a long-duration mission for six individual station crew members."

The contract modification comes after Alexei Krasnov, Roscosmos director of manned flight programs, announced NASA would have to pay $51 million per Soyuz spacecraft passenger on trips to the space station.

RIA Novosti said NASA and Russia previously agreed to a $719 million deal in 2007 that included 15 seats and 5.6 tons of cargo to be transported on Soyuz flights to the orbital site.