Saudi Arabia’s sovereign wealth fund signed an agreement to invest US$1 billion in aspiring U.S. electric-car maker, Lucid Motors Inc. Tesla shares fell.

The deal would give Lucid the funding to take it through to the commercial launch of the Silicon Valley-based start-up’s first electric vehicle, the Lucid Air, in 2020, the Public Investment Fund said in a statement.

The deal between PIF and Lucid adds to the uncertainty surrounding Tesla, whose Chief Executive Officer Elon Musk tweeted on Aug. 7 that he’d secured funding to take the firm private. Musk later backtracked his tweet, while saying the Saudi wealth fund had expressed interest in helping take Tesla private. The Saudi fund had previously built up a stake of just under 5 per cent in Tesla.

“By investing in the rapidly expanding electric vehicle market, PIF is gaining exposure to long-term growth opportunities, supporting innovation and technological development and driving revenue and sectoral diversification for the Kingdom of Saudi Arabia,” according to the PIF statement.

Tesla shares extended losses in pre-market trade, and were down 2.1 per cent at 9:20 a.m. New York.