Nov 30 (Reuters) - NASA has indefinitely postponed a spacewalk planned for Tuesday by two astronauts outside the International Space Station, citing a "debris notification" for the orbiting research laboratory. Astronauts Thomas Marshburn and Kayla had been due to venture outside the space station to replace a failed antenna, facing what NASA officials had said was a slightly elevated risk posed by debris left over from a Russian anti-satellite missile test weeks ago. It was not immediately clear whether the debris NASA referred to in its Twitter announcement of the delayed spacewalk was related to the missile test.