Treasury Secretary Steven Mnuchin said the massive stimulus package the Trump administration is proposing would pump $1 trillion into the coronavirus-ravaged U.S. economy, through a combination of direct tax relief and grants and loans to struggling businesses.

"It's a big number," he said, but "this is a very unique situation." Mnuchin said the package would be paid for with borrowed money, arguing that with historically-low interest rates deficits weren't an immediate issue.

The measure would include more than $500 billion in "general stimulus," a congressional aide said, or direct tax cuts for households, which President Donald Trump and Mnuchin said Tuesday would be in the form of rebate checks. An additional $200 billion would be for expanded loans to small businesses, plus some $50 billion in aid to the cash-strapped airline industry.

Mnuchin discussed the proposal Tuesday at Senate Republicans' weekly policy lunch. Both the administration official and congressional aide spoke on condition of anonymity to discuss plans that haven't been made public yet in detail.

Trump had been seeking a payroll tax holiday through the end of the year. Various iterations have been discussed, ranging from total elimination of the 6.2 percent tax paid by workers and employers, at a roughly $800 billion cost, to smaller cuts in just the workers' share of the tax.