WASHINGTON, Nov 20 - Federal Reserve Chairman Alan Greenspan on Thursday said it was "imperative" that emerging protectionism be vanquished before it hurts globalization, which is key to the U.S. coping with a record trade gap. "Should globalization be allowed to proceed and thereby create an ever more flexible international financial system, history suggests that current imbalances will be defused with little disruption," he said in remarks prepared for a monetary conference sponsored by the Cato Institute and The Economist magazine. "Some clouds of emerging protectionism have become increasingly visible on today's horizon," he said, saying this could "significantly erode" the flexibility of the global economy. "Consequently, it is imperative that creeping protectionism be thwarted and reversed," the Fed chief said.||