Canadian Labour Minister Steven MacKinnon has rejected a request by Canadian National Railway to initiate binding arbitration in a labor dispute with the Teamsters union, a spokesman for the minister said on Thursday.

In a letter to CN Rail's lawyers, MacKinnon said it was the shared responsibility of the company and the union to negotiate in good faith. The letter, sent on Wednesday, was released by the Teamsters.

Talks between CN Railway and Canadian Pacific Kansas City - the country's two largest rail companies - and the Teamsters are deadlocked, with each side blaming the other.

CN Rail said it was disappointed by MacKinnon's decision, saying he would have to reconsider if the union did not "get serious and engage meaningfully at the negotiating table".