White House Press Secretary Jay Carney with payroll tax countdown clock. Charles Dharapak/AP Photo

In the latest effort to ramp up pressure on Congress to extend the payroll tax cut, the White House today unveiled a digital clock counting down to the year-end deadline.

The clock makes clear the president's position on what will happen if the tax holiday is allowed to expire. The clock says, "If Congress doesn't act, middle class taxes increase in," followed by the number of days, hours, minutes and seconds until the tax cut ends).

The clock was first shown in the White House briefing room just moments after President Obama made a public plea for lawmakers to extend and expand the payroll tax cut, saying failure to do so would cost middle-class families $1,000 next year and raise taxes on 160 million Americans.

"What this clock dramatizes is that there isn't a lot of time and that Congress needs to act to do the right thing," White House Press Secretary Jay Carney told reporters. "We can't afford to let that clock go to zero."

The White House has not always been so fond of countdown clocks. Carney was not nearly as enthusiastic about the clocks during this summer's debt ceiling debate that counted down to default.

"The issue we had with the debt ceiling countdown clock is that … it could have a negative impact in raising the specter, which we hoped would never be raised, of the United States defaulting on its obligations, which would have the impact, if it were to come to pass, of causing global economic chaos," Carney said today.

"This is quite different. This is about whether or not 160 million Americans, working-class, middle-class Americans, are going to have their taxes go up on Jan. 1 because Congress refuses to act."