US President Barack Obama has played down the possibility of a breach in national security as a result of the sex scandal that ensnared former CIA Director David Petraeus and a top military commander in Afghanistan, General John Allen. Obama made his first public comments on the growing scandal around two of the US's most well-known generals. The scandal has rocked the Washington security establishment, but Obama said he had seen no evidence it had harmed the security of the nation or its troops.