STOCKHOLM, Jan 10 (Reuters) - Shares in Sweden's Skanska eased on Wednesday after the construction company late on Tuesday announced property value writedowns, mainly at its U.S commercial development business.

Shares in the Nordic region's biggest builder, and one of the biggest in the United States, were down 3% at 171 crowns in early trade, taking a year-to-date drop to 6%.

Skanska is in the fourth quarter booking 2.0 billion crowns ($195 million) worth of impairments and changes in fair market values in its Commercial Property Development, Residential Development and Investment Properties operations.

"The continued weakness in the property markets has led to challenges in assessing the value of property assets," it said in a statement after market close in Stockholm on Tuesday.

"For Commercial Property Development, total impairments amount to 1.4 billion crowns, which is primarily driven by the U.S. portfolio. The U.S. remains the weakest geography," it said.

Skanska, which is due to report full-year results on Feb. 9, said it had also, besides the impairment charges, reduced surplus value in Commercial Property Development by 1.6 billion crowns with no impact on fourth-quarter results. ($1 = 10.2470 Swedish crowns) (Reporting by Anna Ringstrom, editing by Terje Solsvik)