Yellen warns of 'financial crisis' if US defaults on debt

US Treasury Secretary Janet Yellen warned on Friday that the United States could see a recession and "cause a global financial crisis" if it defaults on payments, as Congress heads toward a clash over raising the debt limit.

Yellen's comments to CNN in Senegal come as the US Treasury started taking "extraordinary measures" this week to avert a default as the country reached its $31.4 trillion debt ceiling. But such tools can only help for a limited time, likely no longer than six months, according to the Treasury.

Yellen noted that the actual day on which the Treasury would no longer be able to use these measures is "quite uncertain," and could come as early as June. If the measures were exhausted and Congress fails to raise the debt limit, the US could see a downgrading of its debt "at minimum," Yellen said.

"If that happened, our borrowing costs would increase, and every American would see that their borrowing costs would increase as well," she added. "On top of that, a failure to make payments that are due, whether it's to bondholders or to social security recipients, or to our military, would undoubtedly cause a recession in the US economy and could cause a global financial crisis," Yellen said.

It added that Biden would not negotiate with hardline Republicans over their "risky and dangerous" opposition to increased borrowing for programs Congress already authorised.