By Matthew Benjamin and Mark Drajem

June 13 (Bloomberg) -- After six decades of ever-expanding international commerce, the high tide of free trade is ebbing.

As tens of thousands of South Koreans protest U.S. beef imports, rising commodity prices push nations to keep more food for domestic consumption and the U.S. chooses a new president who might be less supportive of free trade than his immediate predecessors, the world may be facing the end of a cycle that began in the immediate aftermath of World War II.

The liberalization of global trade has come ``to a screeching halt,'' said Fred Bergsten, director of the Peterson Institute for International Economics in Washington. ``It'll take years to rebuild the foundations of free-trade policy.''

The cause is more political than economic. ``This is a challenging time to be in the pro-trade wing of any party in virtually any country,'' U.S. Trade Representative Susan Schwab said June 12 at the U.S. Chamber of Commerce. ``It's hard to be for open trade, whether you are in India or the European Union or in China.''