17 May 2012 Last updated at 14:45

LaShawn Merritt determined to dominate 400m

Olympic 400m champion LaShawn Merritt, who failed a drugs test in 2009, says he is determined to maintain his country's illustrious legacy in the sport by defending his title at London 2012.

The American became the first big name to fall foul of the International Olympic Committee's (IOC) "next Games" ban which was eventually overturned at the Court of Arbitration for Sport (Cas).

Merritt says he is ready to deal with the attention he will receive in London should he defend his title, insisting he did not "intentionally do anything to cheat".