U.S. RELYING ON MEK

"... the MEK (Mujahideen-e Khalq) is the largest and the best-organized Iranian opposition group, with realistic estimates between 6,000 to 10,000 fighters, members and supporters combined. More importantly, the MEK demonstrated its ability to deliver reliable information when it revealed, on August 14, 2002, that the Islamic Republic possessed an advanced nuclear program that included facilities at Natanz and Arak. The MEK now finds support within parts of the American government as a "third option".
http://www.atimes.com/atimes/Middle_East/GK18Ak02.html