TORONTO, March 12 (Reuters) - U.S. Ambassador to Canada Pete Hoekstra said Washington wants to renew the U.S.-Mexico-Canada trade pact but faces resistance from Canada, underscoring uncertainty as a mandatory July 1 review approaches.

Speaking on Thursday at the Canadian Crops Convention in Toronto, he said the U.S. believes the USMCA pact, known as CUSMA in Canada, has worked well but there have been no "substantive" talks with Canada since October.

The Canadian minister responsible for Canada-U.S. trade met with his counterpart, U.S. Trade Representative Jamieson Greer, last week.

"I think we want to get to an agreement, but we are facing some headwinds in the negotiations," Hoekstra said, citing a lack of "substantive" discussions since October.

A representative for the Canadian minister responsible for U.S. trade did not immediately respond to a request for comment.

Hoekstra said:

* Canada should do everything it can to get into the lowesttariff buckets. * The U.S. is looking for coalitions with countries thatwill make sure that if there are trade agreements, then thenon-tariff trade barriers are removed. * U.S. President Donald Trump has said there will be sometariff for getting access to the U.S. market so the Canadiangovernment and businesses should make the case why it isbeneficial for the U.S. to do business with Canada at the lowesttariff rate. * Canada and the U.S. can also work more closely on energy.The U.S. already imports a lot of oil and natural gas fromCanada, the U.S. processes much of this energy, and it wouldwant to expand the partnership. * Canada should also build a stockpile of critical mineralsin Canada or the U.S. to use during emergencies. Canada has manycritical minerals and it should develop a full supply chain tobecome an ideal partner for the U.S.