Mr Musk is the major shareholder in both firms. Tesla's cash situation has taken on additional urgency with the US$2.6 billion SolarCity deal announced on Aug. 1. Mr Musk also said on Wednesday that Tesla plans to release an update of its partly automated self-driving system "in a few weeks". US regulators are probing a May 7 fatality in Florida in which a driver using Tesla's Autopilot system crashed into a truck. The timing of the SEC filing on Tesla's fundraising plans "reinforces the need for SolarCity to have quick access to capital," Barclays analyst Brian Johnson said. The document also disclosed that Mr Musk discussed a potential Tesla-SolarCity merger in February with SolarCity's CEO, Lyndon Rive, who is also Mr Musk's cousin. At a subsequent special meeting on Feb. 29, the Tesla board rejected a proposal to evaluate a merger, according to the filing.