In testimony before Congress Tuesday, beleaguered Postmaster General John E. Potter stated that last month's nationwide deployment of 25,000 additional letter carriers, a controversial move designed to stem demoralizing mail loss, has been an unmitigated success. 'We're losing fewer and fewer packages every day,' said Potter, rebuffing critics who claim the increase has failed to stabilize the country's most troubled routes. 'We ask the public to be patient. The American people have to keep in mind that we still lack the resources to deliver on Sundays.' Potter drew additional fire from lawmakers after he announced plans to scale back the number of active-duty postal workers right before the holiday season. 