By David Shepardson and Lisa Baertlein WASHINGTON/LOS ANGELES (Reuters) -President Joe Biden’s administration on Tuesday made contingency plans aiming to ensure deliveries of critical goods in the event of a shutdown of the U.S. rail system while pressing railroads and unions to reach a deal to avoid a work stoppage affecting freight and passenger service. The potential shutdown, which could come as early as Friday, could freeze almost 30% of U.S. cargo shipments, stoke inflation, impede supplies of food and fuel, cost the U.S. economy about $2 billion per day and cause transportation woes. Ra…