WASHINGTON, Jan 14 (Reuters) - U.S. existing home sales accelerated in December, boosted by lower mortgage rates and slow growth in house prices.

Home sales jumped 5.1% last month to a seasonally-adjusted annual rate of 4.35 million units, the National Association of Realtors said on Wednesday. Economists polled by Reuters had forecast home resales would rise to a rate of 4.21 million units. Home sales increased 1.4% on a year-over-year basis.

"In the fourth quarter, conditions began improving, with lower mortgage rates and slower home price growth," Lawrence Yun, the NAR's chief economist, said in a statement. "Inventory levels remain tight, with fewer sellers feeling eager to move, homeowners are taking their time deciding when to list or delist their homes."

Mortgage rates dropped in 2025 though they remain considerably higher than they were three years ago. President Donald Trump last week ordered the Federal Housing Finance Agency, which oversees mortgage finance giants Fannie Mae and Freddie Mac, to purchase $200 billion of bonds issued by the two companies in a bid to bring down mortgage rates.

Analysts expect the mortgage purchases to have a modest impact. Mortgage rates, which track the benchmark 10-year Treasury yield, remain elevated.

The inventory of existing homes rose 3.5% from a year ago to 1.18 million units in December. At December's sales pace, it would take 3.3 months to exhaust the current inventory of existing homes, up from 3.2 months a year ago.

The median existing home price last month increased 0.4% from a year ago to $405,400. Trump also has proposed banning institutional investors from buying single-family homes to improve affordability.

(Reporting by Lucia Mutikani; Editing by Paul Simao)

((Lucia.Mutikani@thomsonreuters.com))