Congress faces an Oct. 18 deadline for raising the U.S. debt ceiling.

If it is not increased by that date, the government will find itself in an “impossible situation,” Treasury Secretary Janet Yellen said during congressional testimony Thursday.

“The Treasury has been directed by Congress to pay all of the government’s bills, to use the tax revenues that are available and without that to issue debt, and the debt ceiling will make it impossible for us to do that,” Yellen said.

That would be catastrophic for American families, she said.

“Nearly 50 million seniors could stop receiving Social Security payments or see them delayed,” Yellen said.

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The country’s debt ceiling is similar to an individual’s credit card limit. As the money owed increases, the government must raise the debt limit, due to the fact that more is spent than the amount that comes in from taxes.

The issue faced by the government now has been compared with 2011, when the debt ceiling wasn’t raised until the last minute.

At that time, whether or not the government could continue to make Social Security payments was also called into question.

Just as they did then, certain Social Security experts have sought to debunk the idea that the program will not have the funds available to pay benefits.

Among them is Jason Fichtner, vice president and chief economist at the Bipartisan Policy Center, who has served in several senior positions in the Social Security Administration.

The reason Fichtner and others believe so comes down, in part, to the way U.S. Treasury bonds used to pay Social Security benefits are handled.

Generally, those funds are invested in intergovernmental bonds and exchanged for public debt and then cash when the government needs to issue checks to beneficiaries. All of that can happen without exceeding the debt limit, Fichtner said.

There are also dedicated trust funds that can only be used to pay for Social Security benefits that are independent of the debt ceiling.

“They can prioritize Social Security payments,” Fichtner said. “They can do it legally, and they will do it.”

However, running up against the debt ceiling deadline could still have consequences for Social Security beneficiaries.

“If a debt ceiling and a shutdown were to happen at the same time, benefit checks would still go out,” Fichtner said. “They might be delayed, but new claims could not be processed.”

Notably, the government has been anticipating this kind of scenario, which is evident in congressional testimony and Federal Reserve meetings, Fichtner said.

A 2011 House of Representatives report detailed how the government has run so-called “tabletop exercises” as part of its debt ceiling contingency plans to identify how government payments including Social Security and veteran’s benefits could be prioritized.

However, certain recent presidential administrations have perpetuated the idea that if you do not increase the debt ceiling, Social Security checks will not go out.

In that way, they are trying to “weaponize Social Security” and create leverage in the debt ceiling negotiations, Fichtner said.

“I’m not saying you shouldn’t raise the debt ceiling,” Fichtner said. “But let’s be honest about what happens.”

Yellen recently expressed support for removing the debt ceiling from Congress’ control.