As Ontario Premier Doug Ford heads to Washington, he is warning the federal government not to give ground on measures protecting the agriculture sector during talks to renegotiate the North American Free Trade Agreement.

Ford is due to meet Canada's NAFTA negotiators in the U.S. capital on Wednesday to be briefed on the status of the talks. It's his first trip to Washington since becoming premier in June.

Ford is making the trip to meet federal officials and "make the case that any NAFTA deal must protect Ontario jobs in both auto and agriculture sectors," he said in a speech to hundreds of farmers on Tuesday.

"I won't mix words when I go down there because farm jobs are not a bargaining chip. Not now, not ever," Ford said in Pain Court, Ont., at the opening ceremonies of the International Plowing Match, an annual event celebrating Ontario agriculture.

Asked by reporters for more details, Ford said, "I don't want any farmer used as a bargaining chip, be it supply management."

Minister of Foreign Affairs Chrystia Freeland, right, sits for a meeting with Ford in Toronto, on June 14. (Nathan Denette/Canadian Press)

Sources have told CBC News that Canada is willing to make concessions on dairy supply management which would allow American farmers to sell more products north of the border.

Ford said his message to Prime Minister Justin Trudeau's government is: "Don't compromise, because we have to protect the farmers."

It's a shift in tone from Ford's previous pledges of unwavering support for the federal government on the NAFTA talks. It comes just a day after the federal Conservatives vowed to ramp up their criticism of how the government has handled the negotiations.

In June, just a week after winning the provincial election, Ford spoke of "Ontario's government standing shoulder to shoulder with our federal counterparts," in a joint news conference with Foreign Affairs Minister Chrystia Freeland.

"We must stand together during these critical negotiations because there is so much at stake," he said.

I will be going to Washington D.C. on Wednesday, accompanied by Minister <a href="https://twitter.com/mppjimwilson?ref_src=twsrc%5Etfw">@mppjimwilson</a>, to support the work our federal partners have been doing to reach a NAFTA deal. Ontario is open for business, and our government will always stand up for Ontario workers. <a href="https://twitter.com/hashtag/onpoli?src=hash&ref_src=twsrc%5Etfw">#onpoli</a> <a href="https://twitter.com/hashtag/cdnpoli?src=hash&ref_src=twsrc%5Etfw">#cdnpoli</a> —@fordnation

Freeland is also heading to Washington this week in an effort to strike a final deal. She'll continue direct negotiations with her counterpart, United States Trade Representative Robert Lighthizer.

On Tuesday, despite urging the Trudeau government not to compromise, Ford insisted he still stands "shoulder to shoulder" with Ottawa on NAFTA.

Officials in Ottawa say they welcome Ford's interest in the NAFTA talks and see his contribution as useful. Ontario government sources tell CBC News that Ford has a strong relationship with the U.S. ambassador to Canada, Kelly Craft.

Since becoming premier, Ford has made direct contact with a number of U.S. governors to ensure their backing for a trade deal. His predecessor Kathleen Wynne spoke or met with more than 30 governors in the year and a half after the inauguration of U.S. President Donald Trump to try to promote the mutual benefits of NAFTA.

The U.S. is trying to extract some concessions from Canada on the dairy front, demanding more access to a market that is largely protected from imports by supply management. Trudeau has said repeatedly that he will not dismantle the country's farm policies.