Bin Laden did urge his followers to scope out opportunities to attack President Obama or Petraeus while they were in Afghanistan. At the time, Petraeus was the commanding general of NATO soldiers in Afghanistan.
Bin Laden noted snidely that killing Obama would pave the way for Vice President Joe Biden to assume the presidency. The al Qaeda leader said Biden was "totally unprepared" for the job.
http://www.cnn.com/2012/03/16/opinion/bergen-bin-laden-final-writings/index.html?hpt=hp_c1
