Updated: 7:55 p.m.

All 51 Senate Democrats and two independents signed a letter Wednesday opposing Speaker John Boehner’s deficit reduction plan, setting up a showdown if the House manages to pass it Thursday.

The Democrats warned that the proposal’s $900 billion debt ceiling increase would “put America at risk” and “force us once against to face the threat of default” in five or six months, potentially leading to a downgrade of the debt.

“In addition to risking a downgrade and catastrophic default, we are concerned that in five or six months, the House will once again hold the economy captive and refuse to avoid another default unless we accept unbalanced, deep cuts to programs like Medicare and Social Security, without asking anything of the wealthiest Americans,” they wrote.