While the real long-term interest rate will not rise immediately, the committee concluded, “such a fiscal path could force real rates notably higher at some point in the future.”

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In some ways, ballooning deficits should not matter. Deficits are a useful way for governments to use public spending to stimulate the economy when private demand is weak. This works as long as a country closes its deficit and pays back its borrowings after its economy starts to recover.

The trouble is that government borrowing risks crowding out private investment, driving up interest rates and potentially slowing a recovery still trying to take hold. That is why the Federal Reserve announced an extraordinary policy this year to buy back existing long-term debt  $300 billion over six months  to drive down yields. The strategy worked for a while, but now the impact of that decision appears to be wearing off as long-term interest rates tick up again.

Then there is the concern that the interest the government must pay on its debt obligations may become unsustainable or weigh on future generations. The Congressional Budget Office expects interest payments to more than quadruple in the next decade as Washington borrows and spends, to $806 billion by 2019 from $172 billion next year.

“You’re just paying more and more interest and having to borrow more and more money to pay the interest,” said Charles S. Konigsberg, chief budget counsel for the Concord Coalition, which advocates lower deficits. “It diverts a tremendous amount of resources, of taxpayer dollars.”

Of course, no one is suggesting the United States will have problems paying the interest on its debt. On Wednesday, even as it announced its huge financing needs for the latest quarter, the Treasury said financial markets could accommodate the flood of new bonds. “We feel confident that we can address these large borrowing needs,” said Karthik Ramanathan, the Treasury’s acting assistant secretary for financial markets.

One worry, however, is that there are fewer eager lenders to buy all that American debt. Most of the world is in recession, and other nations have rising borrowing needs as well. As other nations’ surpluses turn to deficits, America will face competition in global financial markets for its borrowing needs. For the moment, the United States is actually benefiting from a flight to quality into Treasuries brought on by the global financial crisis, which helped reduce rates to record lows this winter. But the influx will not continue forever.