Opponents of Iran's initial agreement to curb its nuclear program are being "disingenuous" when they say the deal could still allow the country to build nuclear weapons, the head of the Central Intelligence Agency said on Tuesday.

The initial accord reached last week between Iran and major world powers - which would lift crippling economic sanctions in exchange for Iran's agreement to step back from developing nuclear weapons - is likely the most realistic deal that could be reached, CIA Director John Brennan told an audience of students and faculty at Harvard University in Cambridge, Massachusetts, just outside Boston. "The individuals who say that this deal provides a pathway for Iran to a bomb are being wholly disingenuous, in my view, if they know the facts and understand what is required for a program," Brennan said at Harvard's John F. Kennedy School of Government. "I certainly am pleasantly surprised that the Iranians have agreed to so much here."