A plan unveiled by U.S. Democrats on Wednesday would levy new taxes on billionaires, which would help pay for President Joe Biden's proposed spending bill expanding social services and tackling climate change.The so-called billionaires tax, announced by Senate Finance Committee Chairman Ron Wyden, is paired with a proposed 15% corporate minimum tax targeting big, profitable companies that now seem to get away with paying little or no taxes. Proponents, including Democratic Senator Elizabeth Warren, say the measure would curb tax avoidance by corporations and the super-rich, and could generate hundreds of billions of dollars to pay for Biden's "Build Back Better" legislation, which is expected to cost between $1.5 trillion and $2 trillion.The White House backs the corporate minimum tax, which would dovetail with a global corporate minimum tax recently agreed by 136 countries.The billionaires tax, which would take effect in 2022, would affect roughly 700 taxpayers with over $1 billion in assets or $100 million in annual income for three consecutive years.Republican Senate Minority Leader Mitch McConnell on Tuesday said Americans were not interested in higher taxes."Well, the larger issue is whether the country needs a big tax increase. [flash] The American people are not asking for any of this."At least one billionaire, Tesla founder Elon Musk, is unhappy with the plan.As reports of the proposal swirled earlier this week, Musk tweeted, "Eventually, they run out of other people’s money and then they come for you."An analysis by the Washington Post calculated that Musk might owe as much as $50 billion based on his ownership of stock in Tesla and other firms.