Treasury Secretary Timothy Geithner said today that U.S. lawmakers must agree to increase the debt limit, The Wall Street Journal reported.

The United States has “unsustainable” budget deficits, and the country faces no alternative but to cut them, Geithner said to an audience at the Council on Foreign Relations. Political consensus has come around to this view, he said, and despite some discussion to the contrary, politicians will agree to raise the debt cap, he said.

He called the debate on whether to increase the debt limit “ridiculous” and “irresponsible.” Investors are still confident in the United States, he said.

In a letter written to Geithner, Matthew Zames, managing director of J.P. Morgan and chairman of the Treasury Borrowing Advisory Committee, said failure to raise the debt limit could trigger “another catastrophic financial crisis,” Reuters reported.

Zames warned that a default by the U.S. Treasury “or even an extended delay in raising the debt ceiling could lead to a downgrade of the U.S. sovereign credit rating.”