The International Space Station (ISS) will be de-orbited and sunk in the Pacific Ocean after 2020 like its Russian predecessor Mir, Russian Space Agency (Roscosmos) Deputy Head Vitaly Davydov said on Wednesday.

"We will be forced to sink the ISS. We cannot leave it in orbit as it is a very complicated and a heavy object. There must be no space waste from it," Davydov said in an interview posted on the Roscosmos website.

"We have agreed with our partners that the ISS would function roughly until 2020," he said adding the station's life was initially estimated at 15 years.

The ISS has been functioning for 13 years now after receiving numerous international space expeditions.

Asked whether a new space station will be built, Davydov said "there are several possibilities."

The Mir space station was in operation from 1983 to 1998 before being sunk in the Pacific Ocean in a "spacecraft cemetery" not far from Christmas Island in 2000.

The agreement to construct the ISS was signed January 29, 1998 in Washington by representatives from Canada, members of the European Space Agency (ESA), Japan, Russia and the United States.