WASHINGTON (REUTERS) - US President Joe Biden will propose a minimum tax on billionaires as part of the fiscal 2023 budget that is expected to be unveiled on Monday (March 28), a document released by the White House showed.

Biden's "Billionaire Minimum Income Tax" would set a 20 per cent minimum tax rate on households worth more than US$100 million (S$136 million), in a plan that would mostly target the United States' more than 700 billionaires, according to a White House fact sheet released on Saturday.

The plan would require such households to pay the minimum tax of 20 per cent on all of their income including unrealised investment income that is now untaxed, the fact sheet said.

The tax will help reduce the budget deficit by about US$360 billion in the next decade, the fact sheet added.

Senate Democrats last autumn had proposed a billionaires tax to help pay for Biden's social and climate-change known as "Build Back Better" although the spending package did not move forward due to insufficient support in the Senate.