Mexico said Wednesday it is willing to talk about tough issues in the renegotiation of the North American Free Trade Agreement, which is set to start Aug. 16.

Canada has strongly opposed a U.S. proposal to eliminate bi-national dispute resolution panels in which experts now review decisions to impose tariffs or quotas. But Mexican Economy Secretary Ildefonso Guajardo said he isn't taking an immediate position on the panels, though he adds that Mexico wants to "modernize" the process.

"I don't think that when you start negotiations, it does any good to shadow box," Guajardo said, in refusing to fix an initial position.

Guajardo said Mexico would be willing to put stronger labor and environmental guarantees in the text of NAFTA. The issues were previously relegated to weak "side agreements."

President Donald Trump meets with Mexican President Enrique Pena Nieto at the G20 Summit, Friday, July 7, 2017, in Hamburg. (AP Photo/Evan Vucci)

Mexico also wants the energy sector included in the agreement. It wasn't covered by the original 1994 trade pact between the three countries.

Guajardo also made it clear that while Mexico wants talks on immigration issues, it won't try to inject broader issues into NAFTA, but would rather focus on improving some kind of temporary visa program for workers.

The government said in a text of its negotiating goals that it wanted to "expand the categories for temporary visas for business people ... and look for innovative mechanisms for the free movement of labor."

As for rules of origin — the regional content required for products to be considered "made in North America" — Guajardo said Mexico is open to "fine adjustment and constant dialogue."