(Reuters) - Tesla Inc TSLA.O Chief Executive Officer Elon Musk said on Monday improvements unveiled at the electric-car maker's "Battery Day" event would not reach serious high-volume production until 2022.

The company’s shares fell nearly 4% to $432 in extended trade.

“This affects long-term production, especially Semi, Cybertruck & Roadster, but what we announce will not reach serious high-volume production until 2022,” Musk tweeted, ahead of the event scheduled to take place on Tuesday.

Musk also said Tesla intends to increase battery cell purchases from suppliers Panasonic 6752.T, South Korea's LG Chem 051910.KS and China's CATL 300750.SZ, and possibly with other partners as well.

Despite the cell suppliers’ maximum speed, the automaker still expects significant shortages in 2022 and beyond, he added.

Many analysts expect Musk to unveil battery improvements at the event, extending the automaker's lead over General Motors GM.N, Volkswagen VOWG_p.DE and other rivals.

Tesla’s shares closed 1.6% higher on Monday, helped by a leaked email from Musk that said the company was hopeful of racking up record car deliveries in the third quarter.