There had been a broad assumption that most banks under investigation were suspected of manipulating Libor submissions in the financial crisis period running from 2007-9 to appear healthier than they really were, sometimes allegedly with the implicit nod from policy makers.

CNN: Rate probe turns to four major banks

Regarding withdrawal from Iraq, Gates said the military is planning various options, with the quickest withdrawal being the 16-month period -- ending in May 2010 -- outlined by Obama when he was running for president.

CNN: Gates says missile attacks in Pakistan will continue