WASHINGTON—Rising long-term interest rates are making it more expensive for home buyers, corporations and the U. S government to borrow money, threatening to further stifle an already weak economy.

In just the last two weeks, the rate on a 30-year fixed-rate mortgage has risen from 4.9 percent to 5.6 percent, ending a boom in refinancing and working against a budding recovery in the housing market.

Rates on corporate borrowing have also risen, making it more expensive for companies to expand. And the government has been forced to pay more to finance its deficit.

Since the beginning of the year, historically low mortgage rates have had a twin benefit for the economy: They have allowed Americans to refinance about $1.5 trillion worth of mortgages, thus lowering monthly payments and leaving the homeowners with more money to spend on goods and services. Low rates have also created greater incentive for people to buy homes, despite continuing troubles in the housing market.

The abrupt rise in rates has removed that key stimulant for the economy.

The rise has many causes, some of which reflect good news. As investors have grown more confident about the future, for example, they have become more inclined to put money in risky investments, such as the stock market, rather than lending it to the U. S. government and to government-backed mortgage companies.

But other causes give more reason for worry. Investors around the world are increasingly fearful that Congress and the Obama administration will be unwilling to bring taxes and spending into line in the years ahead. That makes the U. S. government appear to be a riskier borrower, leading those who lend to it to demand higher interest payments.

The Federal Reserve now finds itself in a box. It could try to lower rates by purchasing government debt. It has already said it would buy $1.5 trillion in U. S. Treasuries and mortgage-related securities this year to try to stimulate growth.

But doing so would likely only deepen fears that the Fed will print money to fund government deficits in the future. That possibility — while rejected by Fed officials and many mainstream economists — means that expanding purchases might not have the intended effect of lowering rates. It could even drive them up further.

Rates remain very low by historical levels. But the yield on 10-year Treasury bonds has risen from 3.1 percent on March 14 to almost 4 percent this week. (It edged down Friday to 3.86 percent.)

A wide range of other rates are essentially moving in tandem with that rate, including mortgages. That shift has far-reaching implications.

“Households really have no capacity to afford higher rates at this point,” said Scott Anderson, a senior economist at Wells Fargo. “It affects the cost of any long-term borrowing a consumer or business might do, whether it’s auto loans, mortgages, or business credit.”

The number of refinance transactions has dropped 62 percent since early April, according to a survey by the Mortgage Bankers Association.

“Borrowers who were approved but didn’t lock their rate are just walking away,” said Christopher Cruise, a senior loan officer at GotEHomeLoans in Bethesda, Md. “They could have saved a few hundred dollars a month at last month’s rates, but it makes no sense for them to refinance now.”

Even with the benefits provided by refinancing to homeowners, consumer spending has remained soft. In May, retail sales rose 0.5 percent, the Commerce Department said Thursday. But that number was inflated by a sharp rise in gasoline prices that inflated sales at gas stations.

So far, home purchase activity has been relatively stable, according to a range of indicators. But if the higher mortgage rates persist, it could put a damper on a fragile housing market. Home sales have stabilized in the last few months, though at a very low level, spurred in part by lower rates.

“The increase so far has not really been enough to choke off home buying,” said Jay Brinkmann, chief economist at the Mortgage Bankers Association. He added, though, that “higher rates might lead them to pay a lower price or look for a smaller home.”