Kai Ryssdal: Tomorrow is the exact halfway point of the federal government’s 2011 fiscal year. So it’s appropriate to note that today there finally seems to be agreement on a budget for it. Democrats and Republicans in Congress have come to terms on about $33 billion in cuts to be made over the next six months. That’ll help avoid the first government shutdown in 15 years.

But there’s an item on the Congressional agenda that Wall Street’s a whole lot more worried about. The debt ceiling — the legal limit for how much the Treasury Department’s allowed to borrow — at the moment: $14.3 trillion. A tidy sum, but Treasury’s already right up against it.

Our New York bureau chief Heidi Moore reports.

Heidi Moore: Ever since the financial crisis, Wall Street and Washington have been bickering like an old married couple. And like most married couples, they sort of share a bank account — from the U.S. Treasury. Treasury bonds are the safest investment they can hold; they’re almost like cash. But if the Treasury can’t borrow any more, those bonds will be worthless and the U.S. government would default.

Ward McCarthy: I think all the markets would react adversely.

That’s Ward McCarthy, the chief economist at Jefferies.

McCarthy: It would cause probably massive selling of U.S. Treasurys, and because of the loss of confidence in the U.S. government, it would probably also cause the dollar to fall, and at least the U.S. stock market to fall and probably others as well.

Guy Lebas is a fixed-income strategist at Janney Montgomery Scott. He says Congress has to raise the debt ceiling. The alternative would be a worldwide freeze of credit. We saw that once, in 2008.

Guy Lebas: I suspect that a default of the U.S. government would make Lehman Brothers look like a joke.

Lebas says he “suspects” that because the government has never defaulted on its debt. The idea is so unthinkable that no one in the markets is even contemplating it, says Peter Boockvar. He’s the equity strategist at Miller Tabak.

Peter Boockvar: I’m sure it will get passed, I’m sure it will get raised, just as it has every single time.

Congress has raised the debt ceiling almost every year since 1995. But, as the CEOs of several big financial firms said this week, it’s the wait that’s making them nervous. Treasury predicts ‘debt D-Day’ could come as early as April 15.

In New York, I’m Heidi Moore for Marketplace.