WASHINGTON — The White House will ask Congress on Monday to pass a new minimum tax on billionaires as part of a budget proposal intended to revitalize President Biden’s domestic agenda and reduce the national deficit.

The tax would require that American households worth more than $100 million pay a tax rate of at least 20 percent on their full income, as well as unrealized gains in the value of their liquid assets, such as stocks, bonds and cash, which can accumulate value for years but are taxed only when they are sold.

Mr. Biden’s proposal to impose a tax on billionaires is the first time he has explicitly called for a wealth tax. While many in his party have advocated taxes that target an individual’s wealth — not just income — Mr. Biden has largely steered clear of such proposals in favor of increasing the top marginal income tax […]