Treasury Secretary Janet Yellen is reportedly contacting U.S. business and financial leaders to argue the U.S. defaulting on its debt will have a “catastrophic” impact on the U.S. and global economies.

The calls are being reported by Reuters based on two sources familiar with the matter Monday.

Yellen is also having one-on-one talks with CEOs to warn them about the consequences of the partisan “brinkmanship” on the matter, one sources said.

Yellen says the deadline for the U.S. to default of its debt without an agreement to continue to make payments on it is June 1.