WASHINGTON - THE world is not coming to an end on December 21, 2012, the US space agency insisted on Monday in a rare campaign to dispel widespread rumors fueled by the Internet and a new Hollywood movie.

The latest big screen offering from Sony Picture, 2012, arrives in theaters on Friday, with a US$200 million (S$277 million) production about the end of the world supposedly based on myths backed by the Mayan calendar.

The doomsday scenario revolves around claims that the end of time will come as an obscure Planet X - or Nibiru - heads toward or collides with Earth.

The mysterious planet was supposedly discovered by the Sumerians, according to claims by pseudo-scientists, paranormal activity enthusiasts and Internet theorists.

Some websites accuse Nasa of concealing the truth on the wayward planet's existence, but the US space agency denounced such stories as an 'Internet hoax.' 'There is no factual basis for these claims,' Nasa said in a question-and-answer posting on its website.

If such a collision were real 'astronomers would have been tracking it for at least the past decade, and it would be visible by now to the naked eye,' it added. 'Obviously, it does not exist.' 'Credible scientists worldwide know of no threat associated with 2012,' it insisted, adding that after all, 'our planet has been getting along just fine for more than four billion years.'