U.S. Treasury Secretary Janet Yellen is reaching out to business and financial leaders in the country to explain the "catastrophic" impact a U.S. default on its debt would have on the national and global economies, two sources familiar with the matter said on Monday.

The Treasury secretary is having one-on-one conversations with individual CEOs to warn them about the "dangerous consequences of the current brinkmanship," one of the sources said.

The sources declined to name the CEOs with whom Yellen had spoken in recent days, or provide any other details about their conversations, but one said they included executives in the financial sector and broader economy.