In a recent letter to Sen. Barbara A. Mikulski, a Maryland Democrat, former Social Security commissioner Michael J. Astrue said sequestration could slow the time it takes to reach a decision in a case involving a hearing by a month.

Astrue, who stepped down last month at the end of a six-year term, wrote that customers calling the agency's hotline could be placed on hold for 10 minutes — or wait 30 minutes in an office — before connecting with an agency employee.

He said Social Security would cut roughly 5,000 positions through attrition, terminate more than 1,500 temporary employees and eliminate virtually all overtime under sequestration.

"We would try to prioritize our reductions to avoid furloughs that would further harm services and program integrity efforts; however, the possibility of furloughs remains uncertain at this time," he wrote.

The delivery of Social Security checks is not expected to be affected by the sequester. The agency pays out more than $800 billion in benefits annually — money that was exempted from sequestration. The processing of checks is largely automated.  

Most furloughs or other major cuts at federal agencies would not begin immediately on Friday — Obama acknowledged as much on Monday. If sequestration were replaced in a matter of weeks, most agencies, including Social Security, would be likely to avoid furloughs altogether.

And so while lawmakers are still battling publicly over this week's deadline, the attention has increasingly shifted to March 27, when the current stop-gap budget funding the government runs out of money.

Delaying action on the sequester would allow Democrats and Republicans to gauge the economic and political impact of sequestration and, possibly, replace the cuts along with a broader deal to fund the government for the rest of the year.

"I don't think you'll see the sky fall in on March the first — it's not a cliff," Cardin said. "But it won't take long for people to get pretty angry about it."