Former adviser to three US presidents, Bruce Riedel, has said the most difficult challenge faced by US President Barack Obama is to break Islamabad's relationship with the Taliban and 2011 will be his year of Pakistan, reported BBC on Thursday. In an interview with the BBC, he says breaking Pakistan's relationship with the Afghan Taliban will be the most difficult single thing President Obama confronts in 2011. This will be his year of Pakistan. Can he persuade the Pakistanis to at least reduce the support they have given to the Afghan Taliban and to other terrorist groups like Lashkar-e-Tayyaba. That will be very difficult. The president Obama is going to Pakistan in 2011 and this will be at the height of his agenda. Advocating the use of drone technology against terrorist, Riedel said it is a useful tactic because the drones have put more pressure on Al-Qaeda and its core leadership than anything else we have done since 9/11. The drones, for example, had significant impact on Al-Qaeda's ability to plan operations and to even do propaganda. Let me give you a simple example, Al-Qaeda's No-2 Ayman Al Zawahiri, the Egyptian, used to be the chatty caddy in the international terrorism.