Shares in Tesla tanked by as much as 7.6% in premarket trading Monday after its CEO Elon Musk said he is forming a new American political party, provoking an irate response from US President Donald Trump.

President Donald Trump on Sunday called Elon Musk's plans to form a new political party "ridiculous," launching new barbs at the tech billionaire and saying the Musk ally he once named to lead NASA would have presented a conflict of interest given Musk's business interests in space.

With talks stalling and just three framework agreements announced, President Donald Trump is now planning to set some countries' tariff rate by letter and pressuring its larger trading partners to finalize a deal by August.

President Donald Trump blasted Elon Musk’s bid to start a new political party, as the intensifying feud between the former allies deepens concerns among investors over the implications for Tesla Inc.

CNBC's Steve Sedgwick, Karen Tso and Julianna Tatelbaum discuss Tesla CEO Elon Musk's plans to form a new political party. Musk's announcement has drawn the ire of U.S. President Donald Trump.

In a lengthy Truth Social tirade, Trump said Musk has gone ‘off the rails’ in recent weeks, and repeated his theory that the tech mogul’s problem with the sweeping tax bill signed into law on Friday was its elimination of incentives for electric vehicles.