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Barack Obama announces 2012 re-election bid

US President Barack Obama has announced his intention to stand for a second term in office in 2012.

Mr Obama's team released a video on his official website and sent an e-mail to supporters announcing his plans.

The president has an online network of millions of Americans and his web campaign was widely seen as a key plank of his election success in 2008.

This is an excerpt form the video.