BOGOTA, - Colombians rejected a peace deal with Marxist insurgents in a referendum on Sunday, plunging the nation into uncertainty and dashing President Juan Manuel Santos' dream of ending the 52-year war. The surprise victory for the 'no' camp - by less than half a percentage point - was likely to shatter a sense of international jubilation - from the White House to the Vatican - at what appeared to be the end of the longest-running conflict in the Americas. Before the referendum, Santos was confident of victory. He said a 'no' vote would be 'catastrophic' and that he would return Colombia to war if the deal was rejected. Santos, 53, was due to address the nation at 7 p.m. local time (0000 GMT).