During a feud with President Trump, Tesla Chief Executive Elon Musk announced plans to start his own political party. Shares for his company fell more than 6% Monday.

Elon Musk said he’s carrying out his threat to form a new political party after his fissure with President Donald Trump, announcing on social media that he would form the America Party in response to the president’s sweeping tax cuts law.

The tech billionaire says a new party is needed to break up what he calls a "uniparty" system that features Republicans and Democrats.