MOSCOW (AP) -- The replacement crew for the International Space Station started two days of preflight exams Monday, part of final preparations to relieve the two-man Russian-American crew finishing a six-month mission.

Russian cosmonaut Salizhan Sharipov and U.S. astronaut Leroy Chiao are being tested on manually docking and undocking the Soyuz space craft with the orbiting space station and other maneuvers ahead of the scheduled Oct. 9 launch from Russia's Baikonur cosmodrome.

Russian space officials said last week, however, that a problem with the craft's docking system could delay the launch. Konstantin Kreidenko, a spokesman for the Russian space agency, said Monday that engineers were aiming for an Oct. 11 launch date.

Cosmonaut Yuri Shargin also will travel into space, but is to return 10 days later with the current crew, cosmonaut Gennady Padalka and astronaut Mike Fincke.

Russian space vehicles have provided the only link with the space station since the United States grounded the shuttle fleet after Columbia broke apart over Texas on Feb. 1, 2003, killing all seven astronauts on board.