Senate Democratic leaders have sent a letter to President Obama pledging their support if he raises the debt ceiling unilaterally in the face of Republican resistance.

Support has been growing among Democrats in Congress for Obama to invoke the 14th Amendment or another legal justification for expanding the nation’s borrowing authority without congressional approval.

“In the event that Republicans make good on their threat by failing to act, or by moving unilaterally to pass a debt limit extension only as part of unbalanced or unreasonable legislation, we believe you must be willing to take any lawful steps to ensure that America does not break its promises and trigger a global economic crisis — without Congressional approval, if necessary,” Senate Majority Leader Harry Reid (D-Nev.) and other Democratic leaders wrote in a letter dated Jan. 11.