Tesla's first mass-market electric car, the Model 3, hits production this week

New York

TESLA'S long-awaited mass-market electric car will begin rolling off the assembly line this week. But even as it moves ahead, the carmaker is encountering challenges to its ambitious plans for growth.

On Monday, it acknowledged that it had experienced a "severe shortfall" in production of 100-kilowatt battery packs that use new technologies and are made on new assembly lines.

As a result, Tesla's output of 25,708 cars in the…