As negotiators from a dozen Pacific countries try to hammer out a free trade deal in Atlanta, an east-west divide is emerging in Canada.

Western provinces are coming out in favour of the Trans-Pacific Partnership, which they say will boost their exports to Asia. Eastern provinces, however, are sounding the alarm over the impact a deal could have on the dairy and auto sectors.

Ontario Agriculture Minister Jeff Leal and Ontario Economic Development Minister Brad Duguid wrote a letter this week to Canadian Trade Minister Ed Fast, who is currently at the negotiating table, saying they remain worried about the impact on autos and dairy farmers.

“Our government remains extremely concerned at recent reports from international trade experts, and comments by the Prime Minister, which suggest that the government of Canada is prepared to jeopardize the economic well-being of critical sectors of the economy, in particular Ontario’s agricultural and automotive sectors, in order to finalize a deal,” the Ontario ministers wrote to Fast.

Although the details of the negotiations are secret, Prime Minister Stephen Harper amplified worries that the deal would reduce barriers to foreign automakers -- possibly costing Ontario jobs -- during a leaders’ debate earlier this month. Harper said: “What I say to the auto sector in particular -- I’m not suggesting they will necessarily like everything that is in that, but what I am saying is we simply cannot afford as a country to have our auto sector shut out of global supply chains.”

Quebec, which has the most dairy farmers in Canada, has long sounded the alarm on a deal which could lead to increased competition from other dairy-producing countries.

On Thursday, Alberta premier Rachel Notley told CTV Power Play Thursday that she is “cautiously optimistic that it will be good for Alberta business.”

“I think that, overall, for most Alberta businesses it’s going to be an opportunity for them to increase their trade opportunities,” she said, adding she hasn’t yet seen as many details as she would have liked.

Saskatchewan Premier Brad Wall, meanwhile, issued a statement Wednesday saying “the Saskatchewan government strongly supports Canada's participation in the Trans Pacific Partnership (TPP) negotiations currently underway in Atlanta.”

“Trade accounts for more than 60 per cent of our country's gross domestic product, while exports account for one in five Canadian jobs,” Wall’s statement reads. “Access to global markets is particularly important Saskatchewan, which is one of the most export-dependent jurisdictions in the nation.”

British Columbia supports the negotiations. On B.C.’s Ministry of International Trade website, the province notes that “domestic exports of goods to the other members of the Trans-Pacific Partnership were $18.9 billion, or roughly 60 per cent of the Province’s international exports in 2012.”

“A successful Trans-Pacific Partnership agreement would fuel growth in these numbers and help to continue to foster a growing economy in British Columbia.”

Although the deal could still fall through, sources told CTV earlier this week that Canada has tentatively secured the elimination of tariffs on aerospace exports, medical devices, metals and minerals, petroleum products, potash, steel, chemicals, plastics and industrial machinery.

With files from CTV’s Richard Madan in Atlanta