Some of the richest people in the U.S. are calling for a federal wealth tax.

Financier George Soros, heiresses Regan Pritzker and Abigail Disney and Facebook Inc. co-founder Chris Hughes are among those calling for the levy to help address income inequality and provide funding to address climate change and public health issues.

¡°We are writing to call on all candidates for President, whether they are Republicans or Democrats, to support a moderate wealth tax on the fortunes of the richest one-tenth of the richest 1 percent of Americans ¡ª on us,¡± according to a letter signed by 19 individuals ¡ª one anonymously ¡ª and posted online Monday. ¡°The next dollar of new tax revenue should come from the most financially fortunate, not from middle-income and lower-income Americans.¡±

Democratic presidential candidates Elizabeth Warren, Pete Buttigieg and Beto O¡¯Rourke support the idea, according to the letter. Warren¡¯s proposal calls for a 2 percent tax on assets of $50 million or more, and a further 1 percent on assets over $1 billion. It is estimated to generate nearly $3 trillion in tax revenue over 10 years.

The wealth tax isn¡¯t embraced by all Democrats because many believe it would be difficult to assess objectively the value of wealth like artwork and jewels. There are also concerns that such a tax is unconstitutional because the federal government is prohibited from taxing property, only income.

The New York Times reported on the letter earlier Monday.