VITORIA-GASTEIZ, Spain (Reuters) - Luxembourg's Kim Kirchen of the High Road team won the fourth stage of the Tour of the Basque Country on Thursday.

Kirchen beat his Italian team mate Morris Possoni and Spaniard David Herrero of Karpin in a sprint finish to the 171-km stage from Viana to Vitoria-Gasteiz.

Possoni was part of a breakaway during the stage but Kirchen, also winner of Tuesday's second stage, caught and passed him just before the finish line.

Spain's Alberto Contador of the Astana team retained the overall lead.

Friday's 162-km fifth stage is from Vitoria-Gasteiz to Orio. The race ends on Saturday.

(Editing by Rex Gowar)