As the House readies for a nail-biter vote on House Speaker John Boehner’s (R-Ohio) two-step plan to raise the country’s $14.3 trillion debt ceiling, the Senate is prepared to reject the measure immediately if it passes the House, Senate Majority Leader Harry Reid said Thursday.

“Today the House of Representatives will vote on Speaker Boehner’s short-term plan to raise the debt ceiling,” Reid (D-Nev.) said in remarks on the Senate floor. “As soon as the House completes its vote tonight, the Senate will move to take up that bill. It will be defeated. No Democrat will vote for a short-term Band-Aid that would put our economy at risk and put the nation back in this untenable situation a few short months from now.”

A Thursday-night vote by the Senate on the Boehner plan — if the proposal passes the House — would clear the way for Reid to move forward with his own plan. Reid’s statement also seems to rule out the possibility that the Boehner plan could be used as the vehicle for any debt-limit compromise; Democrats had previously left the door open to amending the proposal so that it would more closely reflect the Reid proposal.

On Wednesday, all 53 members of the Senate Democratic caucus announced in a letter to Boehner their unanimous opposition to his plan, which they argued “would put America at risk, along with every family and business in it.”

Senate Minority Leader Mitch McConnell (R-Ky.) said on Thursday that he was “shocked” that Democrats would unanimously oppose the Boehner plan, arguing that the proposal is “the only piece of legislation that has any chance of preventing this from all happening.

“Democrat leaders and the president himself have endorsed every feature of this legislation except one: and that’s the fact that it doesn’t allow the president to avoid another national debate about spending and debt until after the next presidential election,” McConnell said on the floor. “This assurance is the only thing the president and Senate Democrats are holding out for right now.”

The Reid plan would extend the debt ceiling through the 2012 election, while the Boehner proposal would have Congress revisit the debt-limit issue early next year.

Reid defended his plan – which is also supported by the White House – by pointing to statements from independent economists and credit rating agencies that while a short-term deal would avoid default, it could imperil the country’s creditworthiness.

“Economists have said a short-term deal holds many of the same risks as a technical default,” Reid said. “Democrats are not willing to put our economy on the line like that. Our economy and the financial markets desperately need stability. Speaker Boehner’s bill does not provide it.”