Treasury Secretary Janet Yellen warned Friday that the U.S. government will reach its debt limit next Thursday, and called on Congress to take steps now to avoid a catastrophic default.

“I respectfully urge Congress to act promptly to protect the full faith and credit of the United States,” she said.

Yet it’s been widely reported that House Republicans plan to use the debt limit as leverage to impose drastic changes on economic policy, including possible cuts to Social Security and Medicare.

Policy questions notwithstanding, this is a good opportunity to look at what the debt limit is — and what it isn’t.

Specifically, what it isn’t is a green light for more borrowing.

Although some in Congress would have you believe that’s the crux of the matter, it’s just not the case.

The debt limit involves the federal government’s ability to raise sufficient funds to pay for existing obligations — that is, spending that Congress has already approved or has already allocated funds for.

Which is to say, the debt limit is about paying our bills. That’s something every household with a credit card balance or other outstanding payments will understand.

The debt limit is an archaic rule created in 1917 to give Congress more accountability for the nation’s borrowing.

In modern practice, it’s become a way for Republicans to assert influence over other budgetary matters and squeeze concessions from Democrats.

The problem is that these regular games of chicken flirt with government shutdowns and possible defaults on debt payments — reckless, irresponsible moves that create economic weakness and financial peril.

That’s not to say both parties aren’t entitled to seek economic policy changes. They are.

But holding the U.S. economy hostage at regular intervals is just a bad way to effect change, creating uncertainty at a time when prudent monetary management is needed.

Yellen told Congress her department will take “certain extraordinary measures to prevent the United States from defaulting on its obligations.”

But those efforts will run their course by early June, she said. After that, Congress will need to act.

The national debt has risen under every presidential administration since Herbert Hoover. Congress has raised the debt ceiling at least 90 times over the years.

It went up 18 times under former President Ronald Reagan, eight times under former President Bill Clinton, seven times under former President George W. Bush and five times under former President Barack Obama.

Republicans willingly increased the debt limit three times while former President Donald Trump was in power, and never once threatened to undermine the nation’s finances or shut down the government.

Under President Biden, we’re back to putting a gun to the economy’s head.

There’s a better way.

We could require that all congressional appropriations include authority to secure necessary funds.

Better still, we could just do away with the debt limit because it serves no purpose but to allow some politicians to place their party’s interests ahead of the country’s.

Again, there’s nothing wrong with seeking policy changes. That’s something all lawmakers are entitled to do.

Creating financial crises where none exist, that’s something else entirely.