Tesla CEO Musk said in a tweet that he reached out to Apple during the “darkest days” of development of his company’s Model 3 to talk about a possible a deal. Musk said he planned to discuss the possibility of selling Tesla to Apple for one-tenth of its current value, indicating a valuation of about $60 billion.

Production of the Model 3 began in 2017, around the same time Apple decided to shift from development of a full-fledged Tesla competitor to an underlying self-driving car system. In recent years, Apple has hired a number of ex-Tesla executives who specialize in drive train, car interior and self-driving technology, indicating that the company is once again considering entering the market.

An Apple spokesman didn’t immediately respond to a request for comment.

Apple stock has climbed, while Tesla stock has slipped in response to a Reuters report that Apple is aiming it put a car into production as early as 2024. Apple shares climbed 2.9% to $131.88 on Tuesday.