COPENHAGEN, Dec 6 (Reuters) - PensionDanmark, one of Denmark's largest pension funds, said on Wednesday it had decided to sell its holdings in Tesla (TSLA.O) over the U.S. auto company's refusal to enter into agreements with labour unions.

The decision is part of a growing Nordic movement to force Tesla to sign collective bargaining agreements with Swedish mechanics, who have been on strike since October.

Labour unions in Norway and Denmark this week said they would start blocking transit shipments of Tesla cars meant for the Swedish market.

Tesla has a policy of not agreeing to collective bargaining and says its employees have as good or better terms than those the Swedish union is demanding.

"In the light of the conflict now spreading to Denmark as well as Tesla's recent very categorical refusal to enter a labour union agreement in any country, we have come to the conclusion that we as investors at present hardly can influence the company," the pension fund said in an emailed statement.

"That is why we're now putting Tesla on our exclusion list," it said.

PensionDanmark, which manages pensions for 823,000 Danes, has 317.3 billion Danish crowns ($45.81 billion) under asset management.

The fund did not say how big its holdings in Tesla are.