AP Photo

Renewed international efforts to reign in Iran's atomic program have shrouded another unresolved Middle East nuclear challenger, Syria. The International Atomic Energy Agency's failure to get Damascus to reveal the history of its secret nuclear reactor and related elements raise troubling questions not simply about the Assad regime's nuclear intentions but, more fundamentally, about the ability of the IAEA to act as an effective watchdog. Unless Syria provides a full accounting, its successful stonewalling will only serve further to undermine international efforts to curb proliferation.

US Mideast envoy George Mitchell, left, shakes hands with Syrian President Bashar Assad upon his arrival at the Syrian presidential palace in Damascus, Syria, earlier this year....