Russian cosmonaut Oleg Kononenko is expected to set a world record on Sunday for the duration of space flights with nearly 2-1/2 years in total, Russian news agencies reported.
As expected, at 11:30:08 Moscow time (0830:08 GMT), the 59-year-old Kononenko will exceed the achievement of his compatriot Gennady Padalka, who accumulated a total of 878 days, 11 hours, 29 minutes and 48 seconds over five space flights before retiring in 2017, the state news agency TASS reported.
Kononenko, who is the commander of the Russian space state agency Roscosmos cosmonaut corps, is conducting his fifth space flight. Upon completion of the current expedition, scheduled for Sept 23, Kononenko will have logged 1,110 days in space.
At the age of 34, Kononenko began training as part of the group of cosmonauts selected for the International Space Station (ISS) programme, according to the European Space Agency's website.
He went on his first space flight on April 8, 2008, as part of the 17th main expedition of the ISS, returning to Earth on Oct 24, 2008, the Interfax news agency reported.
The ISS is one of the few international projects on which the United States and Russia still cooperate closely. In December, Roscosmos said that a cross-flight programme with NASA to the ISS had been extended until 2025.
Relations in other areas between the two countries have broken down since Russia's invasion of Ukraine nearly two years ago, to which Washington responded by sending arms to Kyiv and imposing successive rounds of sanctions on Moscow.