By Irene Klotz

(Reuters) - A multinational crew, including a U.S. astronaut who is the oldest and most experienced woman to fly in space, blasted off from Kazakhstan on Thursday for the International Space Station, where it should arrive in two days, a NASA TV broadcast showed.

The Russian Soyuz rocket carrying American Peggy Whitson, Russian cosmonaut Oleg Novitskiy and French astronaut Thomas Pesquet lifted off from the Baikonur Cosmodrome at 3:20 p.m. EST (2020 GMT).

Whitson, 56, a biochemist and NASA's former chief astronaut, is making her third trip to the station, a $100 million research laboratory that flies about 250 miles (420 km) above Earth.

By the time she returns to Earth in six months, she will have accumulated more time in orbit than any other U.S. astronaut, surpassing the 534-day record set in September by astronaut Jeff Williams.

"The most important thing about the station is the friendships and the work we accomplish there," Whitson said during a prelaunch news conference on Wednesday in Kazakhstan.

Novitskiy, 45, who is making his second spaceflight, added: "The station is ... a place where we can demonstrate to the entire world that you can have normal relations, where you can work without being distracted by things that don't really matter."

Joining the veteran fliers is Pesquet, 38, a rookie astronaut representing the European Space Agency.

The crew is due to reach the station at 5:01 p.m. EST (2201 GMT) on Saturday, where it will be greeted by NASA astronaut Shane Kimbrough and Russian flight engineers Sergey Ryzhikov and Andrey Borisenko, who arrived on Oct. 21.

The combined crew will be one of the last six-member teams to live on the station for a while. Beginning in March, Russia plans to cut the number of cosmonauts serving on the station to two from three, following delays in launching a new science laboratory. The Multipurpose Laboratory Module is now expected to be launched in 2018.

(Reporting by Irene Klotz in Houston; Editing by Letitia Stein and Peter Cooney)