Roscosmos director Anatoly Perminov said in an interview with the daily Rossiiskaya Gazeta that the last commercial flights would be made in March 2009 by Charles Simoniy (his second trip) and by a Kazakh national in the fall of 2009.
The Kazakh National Space Agency previously said that a Kazakh cosmonaut would fly to the ISS in October 2009.
Perminov also said Russia would not cancel any space launches slated for 2009 due the global financial crisis.
"I hope that we'll cope. So far we are preparing to make four manned launches, not two, as previously planned, and send five, not four, freight modules into space," he said.
He also said the Russian segment of the ISS included a total of 156 projects, 19 of which have already been completed.
Roscosmos earlier said a Russian space tourist hopeful would miss out on a trip to the ISS in the autumn of 2009, and that a Kazakh cosmonaut would be likely to take his place.