General David Petraeus, architect of the US military surge credited with dramatically reducing violence in Iraq, has said that Pakistan's leaders need to realise that their biggest threat comes from internal extremists, not from neighbouring India.

"It's an intellectually dislocating idea for the institutions of Pakistan," Petraeus, the leader of US Central Command, which oversees the wars in Iraq and Afghanistan, told a forum at the Harvard University on Tuesday, referring to the country's military and political establishment.