Treasury Secretary Steven Mnuchin told CNBC on Wednesday that small businesses throughout the U.S. should not worry about their odds of receiving relief funding from the federal government.

Asked by CNBC's Jim Cramer about the White House's work with the Small Business Administration, Mnuchin said he's confident Congress will approve additional funding on top of the original $350 billion already being distributed.

"Jim, we're raising over $2 trillion for our COVID relief. We're raising it all across the curve and we have tremendous demand for U.S. Treasurys," Mnuchin said. "Everybody wants to buy U.S. Treasurys: It's the safe haven."

"I want to assure all small businesses out there: We will not run out of money. The president has asked us to go back to Congress. We hope they pass this tomorrow or Friday," he added. "And we want to assure everybody if you don't get a loan this week, you'll get a loan next week or the following week. The money will be there."

Congress passed $350 billion in small business funding last month for the Paycheck Protection Program as part of an unprecedented $2 trillion package to try to ease the economic pullback caused by the novel coronavirus and efforts to stanch its spread.

But some small business owners worry about being left out of the pot as big banks, equipped with the scope and staff to push the government's funds out the door, focus on their existing customers. Some, like San Francisco-based Wells Fargo, said Sunday that it likely reached its $10 billion limit based on the applications it had received at the time.

The small business measures approved by Congress and President Donald Trump aim to help companies keep employees on the payroll and manage other expenses during the outbreak. Firms with fewer than 500 employees can use the money to cover salary, wages and benefits, with a maximum loan of $10 million.

The funding is available through Small Business Administration-approved lenders and loan payments will be deferred for six months with the possibility of forgiveness on at least part of what they borrow.

— CNBC's Jacob Pramuk contributed reporting.