While these groups have links with Al Qaeda, the bigger danger to the US is their ability to trigger a major crisis for nuclear-armed Pakistan, including a war with India.
Officials aren't saying which militants, if any, Faisal Shahzad may have met in Pakistan, but focus is intensifying on how interlinked Pakistan militants groups may be. Pakistan and US officials differ in their assessments.
Jihadi training camps in Pakistan – like the one Times Square car bomb suspect Faisal Shahzad said he attended – have taught bombmaking and other skills to militants since the 1980s.
New York Times reporter Davide Rohde has recounted his seven months held captive by a Taliban group in Afghanistan, and argues that convincing Taliban militants to make peace with the US and Kabul will be a tall order.