By Alexandria Sage SAN FRANCISCO (Reuters) - Tesla Inc (TSLA.O) said on Wednesday it was sticking with Chief Executive Elon Musk's revised production targets for its Model 3 electric sedan, but posted its worst-ever quarterly loss, and warned that spending would increase slightly this year. Shares of the Palo Alto, California-based company were down about 0.29 percent in extended trading. Money-losing Tesla's long-term viability depends on annually selling billions of dollars of Model 3s, the new sedan that starts at $35,000, about half the price of its flagship Model S.. Tesla said that net reservations for the new model were stable during the fourth quarter. Production delays have curtailed deliveries of the vehicle to customers - only 1,550 deliveries in the fourth quarter, far below the 4,100 vehicles expected by analysts - meaning revenue from the highly anticipated vehicle has yet to hit Tesla's bottom line.