The head of Canada's largest private-sector union is set to talk NAFTA with one of Donald Trump's most trusted cabinet members.

Jerry Dias, the president of Unifor, will meet with U.S. Commerce Secretary Wilbur Ross, in Washington, on Thursday.

It will be the fourth meeting this year between the pair, who have come to regularly discuss some of the most divisive issues at the NAFTA negotiating table, including the auto sector.

"I'm going to try and find some commonality on auto," Dias said during a phone interview with CBC News.

The sit-down coincides with an inter-session gathering of NAFTA negotiators.

Trade delegations from Canada, the U.S. and Mexico are meeting for five days in the U.S. capital, with talks wrapping up on Friday.

While this is not a formal round of negotiations, officials are hoping to make progress on some of the technical issues ahead of the next official meeting in Montreal, in early 2018.

NAFTA lightning rod

A source with direct knowledge of the talks told CBC News that, this week, chief negotiators are expected to discuss rules of origin, which includes regulations for the auto sector.

Canada and Mexico have bluntly rejected U.S. proposals to dramatically boost made-in-America auto sector requirements.

Experts say the proposals would end up killing jobs in all three countries, with automakers looking to overseas markets to build their products instead.

Dias said he plans to address these concerns with Ross, to "see if we can come up with a more livable number on rules of origin, that the auto industry can live with and that will benefit both of our nations."

Prime Minister Justin Trudeau and Chinese Premier Li Keqiang reach out to shake hands during a meeting at the Great Hall of the People in Beijing, China, on Dec. 4. (Fred Dufour/Reuters)

But as far as formal talks are concerned, Dias is not expecting significant movement on the auto sector anytime soon.

"The auto industry really is the lightning rod for the entire set of NAFTA negotiations, so my guess is that gets resolved at the end."

Dias also suggests the prime minister's recent trip to China may increase Canada's strength at the negotiating table, even though Justin Trudeau returned home without an agreement to launch free trade talks in Asia.

"He went to China to kick the tires, to let the U.S. know that they are serious about finding alternative sources for our products," Dias said.

Trusted Trump advisor

Although Ross is not directly overseeing NAFTA talks for the U.S., he is one of Trump's closest advisers.

When Trudeau visited the White House this fall to talk trade, it was Ross who sat in on the meeting, rather than U.S. Trade Representative Robert Lighthizer.

Trump also stood by Ross, during recent scrutiny of his personal finances, after he was named in the so-called Paradise Papers, examining off-shore tax havens.

Ross has been one of the Trump administration's loudest critics of NAFTA, using media appearances to repeat the president's belief the trade deal has killed thousands of American jobs.