FRANKFURT—The planned opening of Tesla’s first gigafactory in Europe later this year will force local industry to step up its game, Volkswagen Chief Executive Herbert Diess said on Friday. Diess’ comments, made on Twitter, come as Tesla continues work on its plant in Gruenheide, near Berlin, as it awaits final building approval for the 5.8 billion euro ($6.8 billion) site. “Efficiency is key for the transformation of our industry/Germany. Tesla develops in shorter processes, works closer with the best in the industry and takes more risk,” Diess, a known admirer of the electric car pioneer led by Elon Musk, said. Wolfsburg-based Volkswagen, Europe’s largest carmaker, aims to overtake Tesla as the world’s top seller of electric cars by 2025, a claim that is underscored by an ambitious plan to build six large battery factories in Europe by 2030. “Gruenheide will increase competition in Germany—also with Wolfsburg.” The EV maker is …