A year after Washington rescued the big names of American finance, it’s still hard to get a loan. But the problem isn’t just tight-fisted banks.

The continued disarray in debt-securitization markets, which in recent years were the source of roughly 60 percent of all credit in the United States, is making loans scarce and threatening to slow the economic recovery. Many of these markets are operating only because the government is propping them up.

But now the Federal Reserve has put these markets on notice that it plans to withdraw its support for them. Policy makers hope private investors will return to the markets, which imploded during the financial crisis.

The exit will require a delicate balancing act, government officials said.

“You do it incrementally, where and when you think you can, and not sooner,” said Lee Sachs, a counselor to the Treasury secretary, Timothy F. Geithner.