<ul data-eligibleForWebStory="true">Tesla shares decline by about 5% in pre-market trading amid a heated exchange between Donald Trump and Elon Musk.Trump threatens subsidy cuts, criticizing Musk's subsidies and suggesting Musk may have to close his businesses without them.Musk counters Trump's claims, proposing the president should actually cut the subsidies.Speculation rises about Musk forming a new political party, 'America's Party,' with odds currently standing at 40%.