WASHINGTON -- With a nationwide farmworker shortage threatening to leave unharvested fruits and vegetables rotting in fields, the Bush administration has begun quietly rewriting federal regulations to eliminate barriers that restrict how foreign laborers can be brought into the country legally. The urgent effort, under way at the U.S. departments of Homeland Security, State and Labor, is meant to help farm owners caught in a vice between an impossibly complex process to hire legal guest-workers and stepped-up enforcement that has reduced the number of undocumented planters and pickers crossing the border. "It is important for the farm sector to have...