Senate Democrats are unveiling a new billionaires’ tax proposal to help pay for President Joe Biden’s sweeping domestic policy package.

The tax proposed Wednesday would be on the gains of those with more than $1 billion in assets or incomes of more than $100 million a year. And the tax could begin to shore up the big social services and climate change plan Biden is racing to finish this week.

Biden needs to win over key Democrats, including Sen. Kyrsten Sinema of Arizona, who had rejected earlier tax plans.

Biden says his package will be fully paid for and won't raise taxes on anyone earning less than $400,000 a year.