Al Qaeda's affiliate inside Syria is now the best-equipped arm of the terror group in existence today, according to informal assessments by U.S. and Middle East intelligence agencies, a private sector analyst directly familiar with the information told CNN.

Concern about the Syrian al Qaeda-affiliated group Jabhat al-Nusra, also known as the al-Nusra Front, is at an all-time high, according to the analyst, with as many as 10,000 fighters and supporters inside Syria. The United States has designated al-Nusra Front as a terrorist group with links to al Qaeda in Iraq.