New U.S. housing starts unexpectedly fell in December, pulled down by a drop in construction activity for single-family dwellings, a government report showed on Wednesday.

The Commerce Department said housing starts fell 4 percent to a seasonally adjusted annual rate of 557,000 units. Analysts polled by Reuters had expected housing starts to rise to 580,000 units. November's housing starts were revised upwards to 580,000 units from the previously reported 574,000 units. The drop in housing starts was likely the result of unusually cold weather last month.

Groundbreaking activity dropped a record 38.8 percent to an all-time low of 553,000 units for the whole of 2009.

Starts for single-family homes fell 6.9 percent last month to an annual rate of 456,000 units after rising 4.0 percent in November. Groundbreaking for the volatile multifamily segment rose 12.2 percent to a 101,000 unit annual pace, after surging 69.8 percent in November.

Housing is on the mend after a three-year slump and new home construction contributed to economic growth in the third quarter of 2009 for the first time since 2005.

However data such as pending home sales and homebuilder sentiment have hinted at potential weakness in a sector whose collapse triggered the most brutal U.S. recession since the Great Depression of the 1930s.

New building permits, which give a sense of future home construction, rose 10.9 percent to 653,000 units last month, the highest since October 2008. That compared to analysts' forecasts for 590,000 units. For the whole of 2009, permits dropped 36.9 percent, the department said.

The inventory of total houses under construction dropped 3.8 percent to a record low of 511,000 units last month, while the total number of permits authorized but not yet started rose 8.4 percent to 95,800 units.

(Reporting by Lucia Mutikani; Editing by Andrea Ricci)

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