OTTAWA, April 23 (Reuters) - Canada's Competition Bureau on Tuesday said it had identified major competition concerns around the proposed merger between U.S. grains merchant Bunge and Glencore-backed Viterra.

In a statement, the bureau said the deal was "likely to result in substantial anti-competitive effects and a significant loss of rivalry between Viterra and Bunge in agricultural markets in Canada".

The report was sent to Canada's transport ministry, which has until June 2 this year to review the deal. (Reporting by David Ljunggren)