"Tesla & Ford are the only American carmakers not to have gone bankrupt out of 1000's of car startups. Prototypes are easy, production is hard & being cash flow positive is excruciating," Musk said in a tweet on Friday.
Ford CEO Jim Farley responded to his tweet, saying: "Respect".
In 2020, Tesla produced and delivered half a million vehicles. In addition, Model Y production in Shanghai has begun.
Tesla this year also registered its Indian subsidiary with the Registrar of Companies (RoC) in Bengaluru, on 8 January.
"2020 was a defining year for us on many levels. Despite a challenging environment, we've reached an important milestone of producing and delivering 0.5 million cars," Musk had said.
On the other hand, Ford's increased investment is aimed at catching up with the EV market leader Tesla and keep pace with other automakers like GM and Volkswagen.
"We are accelerating our plans right now, breaking constraints, increasing battery capacity, improving our costs and getting more battery electrics into our cycle plan," Ford CEO Farley said last month.