By Doyinsola Oladipo and David Shepardson NEW YORK (Reuters) -Dockworkers on the U.S. East Coast and Gulf Coast began a strike early on Tuesday, their first large-scale stoppage in nearly 50 years, halting the flow of about half the nation's ocean shipping after negotiations for a new labor contract broke down over wages.

Union dockworkers at ports across the U.S. began walking picket lines early Tuesday, snarling the movement of billions of dollars' worth of goods.