"I was dismayed to read this morning that rank-and-file Republicans … are on the fence on whether we should extend this tax break for American families," said Reid. "[R]epublicans are questioning whether the American people need the extra cash. ... They are once again playing politics and putting our economy at risk at a crucial time."

Republicans took a beating in the polls in December when they showed reluctance to extend the tax break — a provision of President Obama's keynote jobs plan — because they objected to the pay-for mechanisms put forth by Democrats that would have raised taxes on Americans earning more than $1 million. The conclusion of the fight was postponed when the parties finally agreed to a short-term two-month extension of the tax cut, which is set to expire in less than month. 

Reid on Monday afternoon described the back-up plan Senate Democrats are preparing in case the House does not extend the cut. 

"Democrats will not give in when it comes to protecting middle class," said Reid. "That’s why we will prepare a fallback plan in case Republicans refuse to cooperate."

The plan described by Reid would extend the payroll tax cut, extend unemployment benefits, "protect seniors on Medicare" and extend "expired tax provision." 

Reid did not say which tax provision their plan would extend.