NEW YORK (Reuters) - The U.S. housing market, already struggling with tight inventory and rising building costs, faces a fresh headwind as 30-year mortgage rates rise close to the 5 percent threshold for the first time in years.

FILE PHOTO: A "For Sale" sign is seen outside a home in Cardiff, California February 22, 2016. REUTERS/Mike Blake/File Photo

Even as home prices have climbed steadily thanks largely to a lack of supply of homes for sale, housing affordability has remained relatively stable thanks to historically low borrowing costs.

But that is changing. Mortgage rates have surged to 4.97 percent from 4.23 percent in January, according to the Mortgage Bankers Association. Including fees, most 30-year mortgage costs have reached 5 percent or higher.

The rise in mortgage rates so far this year means a potential homebuyer would pay about $35,000 more interest on a $220,000 loan over 30 years.

U.S. borrowing costs have risen broadly as the Federal Reserve has raised its benchmark lending rate from near zero three years ago to between 2.00 percent to 2.25 percent after the central bank’s policy meeting last week. It signaled rates would rise further in the months ahead.

The central bank has also been reducing its holdings of mortgage bonds purchased in an unconventional policy adopted during the 2007-2009 credit crisis. Yields on the bonds that exert the most influence on mortgage rates have climbed as investors demand higher compensation on a pickup in inflation and economic growth from the tax cuts enacted last December.

“Higher interest rates is a headwind for housing, but it’s not a major obstacle right now,” said Ward McCarthy, chief economist at Jefferies & Co. in New York.

Some economists believe home loan costs have to increase much higher to cause a slump in housing activity.

“We need to see rates rise another 100 basis points to see a substantial drag,” said Aaron Terrazas, senior economist at Zillow in Seattle.

(Graphic: U.S. home prices vs 30-year mortgage rate - tmsnrt.rs/2KTHG7M)

HOUSING SECTOR SPUTTERS

Residential property sales in 2018 floundered due to low inventory and a land shortage for developers to build new homes.

A dearth of available workers and rising material costs, stemming in part from tariffs, have hampered the sector, analysts said.

Home resales softened this spring, typically the strongest season. They stabilized at 5.34 million annualized units in August, but remained down 1.5 percent from a year ago, according to the National Association of Realtors.

Inventory of existing homes rose to 1.92 million last month, the first increase in three years on a year-over-year basis.

New home sales fell for two straight months before rebounding to an annualized rate of 629,000 in August.

While new home sales make up a smaller portion of the overall housing market, they are seen as more critical to economic growth because they help drive consumer and construction activity.

(Graphic: U.S. home sales - tmsnrt.rs/2N5lnMM)

HOME AFFORDABILITY

Consumers’ demand for a home remains high, and analysts said rising mortgage rates may push some who have been sitting on the sidelines to jump into the game.

“Affordability at least currently is average in this period of time,” McCarthy said. “The rise in mortgage rates has encouraged some people to move into the market now.”

Mortgage applications to buy a home rose 2.6 percent in the week ended Sept. 21, rebounding from a near 11-month low in August, according to MBA data.

Prospective buyers are now pressing sellers to lower prices, McCarthy noted.

“They have moved their sights lower,” he said. “They are bargaining harder.”

Home prices in 20 major U.S. metro areas grew at 5.9 percent annual clip in July. They have slowed for a fourth straight month from a 6.8 percent pace in February, according to S&P/Case Shiller.