A plan for Russia's Soyuz capsule to fly around the International Space Station and take pictures of the US shuttle Discovery and other global spacecraft was deemed too risky, NASA said Tuesday.
"It was kind of a late proposal that we do this," largely because the US shuttle was delayed from its initial November launch plan due to technical problems, said NASA spokesman John Ira Petty.
"The Soyuz that is attached to the station that would have been used is a new type of Soyuz and they (the Russians) were reluctant to add this extra activity," said Petty.
"The risk of failure would have seen three new crew members going home earlier than scheduled," he said, adding that NASA understood and backed the Russians' decision.
Meanwhile, NASA decided to extend the shuttle's mission to the ISS by one day, with a return to Earth now set for March 8, and astronauts completed the installation of the Permanent Multipurpose Module on the underside of the lab.
"The extension day will be devoted to emptying the Permanent Multipurpose Module and moving supplies between Discovery and station," NASA said in a message on the microblogging site Twitter.
A first spacewalk to install preparations for the storage module was completed Monday.
The shuttle blasted off from Kennedy Space Center on February 24, on its final mission into orbit before entering retirement. Discovery is the first of three US shuttles set to become museum pieces later this year.
Endeavour is to lift off on April 19 followed by Atlantis on June 28, marking the official end of the US space shuttle program after 30 years.
The Discovery shuttle's mission now will last 12 days, with a second spacewalk planned for Wednesday.
Explore further: Astronauts to reveal sobering data on asteroid impacts