Biden’s initial and preferred plan has been to increase the corporate tax rate from 21 percent to 28 percent. The increased taxes would help fund roads, bridges, electric vehicles and broadband, but Republicans have disagreed. An increase in corporate taxes would undo the tax cuts signed by former President Donald Trump in 2017.

There is currently no minimum corporate tax on profits, so Biden proposed establishing a 15 percent minimum to give Republicans an alternative to his plan that would not require raising corporate taxes.

Another part of the proposal is revenue that could come from increased IRS enforcement of unpaid taxes, the Associated Press reported. House Speaker Nancy Pelosi suggests the amount could be as high as $1 trillion, but other estimates place it far lower. Both Republicans and Democrats have considered the plan.

For more reporting from the Associated Press, see below.

The offer was made Wednesday to Republican Sen. Shelley Moore Capito of West Virginia as part of the bipartisan negotiations and did not reflect a change in Biden’s overall vision for funding infrastructure, according to a person familiar with the talks who insisted on anonymity to discuss private conversations.

The Washington Post first reported the offer.

On Thursday, Senate Republican leader Mitch McConnell said he spoke with Capito after the session and is “still hoping” to reach a deal with the administration. But he prefers the GOP approach that is eyeing a scaled-down package, paid for by tapping unspent COVID-19 relief funds, rather than taxes.

“Let’s reach an agreement on infrastructure that’s smaller but still significant, and fully paid for,” he said in Paducah, Kentucky.

The president is essentially staking out the principle that profitable corporations should pay income taxes. Many companies can avoid taxes or minimize their bills through a series of credits, deductions and other ways of structuring their income and expenses.

The president has insisted that the middle class should not bear the cost of greater infrastructure spending. Yet a chasm exists in negotiations because Republicans say that corporate tax increases will hinder economic growth.

The idea of imposing a minimum corporate tax is not new from Biden, who proposed the policy during the presidential campaign last year. The center-right Tax Foundation estimated that a minimum tax would subtract 0.21 percent from long-run U.S. gross domestic product.

“He’s been pushing it since the primaries over a year ago,” said George Callas, managing director of of government affairs for the law firm Steptoe and a former tax counsel to House Republicans. Callas said that the minimum tax would mostly hit firms such as electric utilities and telecoms that make substantial capital investments as well as companies that rely on paying their employees with stock.

Biden is seeking roughly $1 trillion in infrastructure spending, down from an initial pitch of $2.3 trillion. Republicans, so far, have countered with only $257 billion in additional spending on infrastructure as part of a $928 billion package, a fraction of what the president says is necessary to compete globally and boost economic growth.

Talks over Biden’s top legislative priority have been moving slowly, a daunting undertaking given the massive infrastructure investment, and time for a deal is running out. The administration has set a June 7 deadline to see clear direction and signs of progress.

Biden and Capito are set to meet again on Friday.