TORONTO, Jan 14 (Reuters) - Goldcorp Inc commenced its formal bid for Osisko Mining Corp on Tuesday, saying that it chose to proceed with the unsolicited offer following a long series of frustrated attempts to engage Osisko in discussions about a possible deal.

In a takeover bid circular, filed with securities regulators on Tuesday, Goldcorp gave details of a series of attempts since 2008 to reach a friendly deal with Osisko.

Goldcorp announced it was launching an unsolicited cash-and-stock bid to acquire its smaller rival Osisko for C$2.6 billion ($2.4 billion) on Monday. If successful, the takeover will give Goldcorp control of Osisko's huge Malartic gold mine in Quebec, along with other assets.

Vancouver-based Goldcorp said it opted to proceed with the unsolicited offer only after having "made repeated and genuine attempts to discuss a mutually beneficial transaction."

Goldcorp said Osisko's management has continually refused to either negotiate, or engage in meaningful dialogue, leading to the current circumstances.

The company said it last tried to reach a deal with Osisko over the summer, but Osisko's board decided to terminate talks about a possible transaction in November.

A spokesman for Osisko was not immediately reachable for comment.