Trade talks with Donald Trump and the race to adopt new rules for legalized pot will dominate the agenda as Canada's premiers gather in Edmonton this week.

With the U.S. president expected to lay out his objectives in renegotiating the North American Free Trade Agreement (NAFTA) as early as today, the annual summer meeting of the Council of the Federation will be seized with ensuring diverse provincial interests are brought to the table when the federal government begins talks next month.

We're not afraid to have NAFTA looked at and negotiated, but I think it's important this doesn't drag on. - Nova Scotia Premier Stephen McNeil

Nova Scotia Premier Stephen McNeil is calling for a united front to promote the provinces' various economic drivers —from oil and hydro to seafood and rubber.

"What we need to make sure of — and I think this would be a common front — is that provinces would be part of that conversation, that this conversation doesn't happen without our input, and telling us what those negotiations look like so we can give them the impact of what it would mean to our respective provinces."

Canada's ambassador to the U.S., David MacNaughton, will take part in Tuesday's session, which will focus primarily on engaging with the U.S. on critical issues like softwood lumber and NAFTA.

"We're not afraid to have NAFTA looked at and negotiated, but I think it's important this doesn't drag on," McNeil said. "We need to make sure investment confidence is still high, recognizing our two countries are linked."

Tuesday's meeting will also include discussions on domestic economic issues such as labour mobility, infrastructure and environmental approvals.

Indigenous leaders boycott

The three-day gathering was to begin today with meetings with five Indigenous groups, but three of the leading groups are boycotting.

The Assembly of First Nations (AFN), the Métis National Council and Inuit Tapiriit Kanatami (ITK) told CBC News Friday they're backing out of the meeting because they believe their groups should be included as equal partners at the Council of the Federation meeting.

Leaders of the three groups have scheduled a news conference in Toronto for 11 a.m. ET.

Two other major Indigenous organizations are still planning to attend: the Congress of Aboriginal Peoples (CAP) and the Native Women's Association of Canada.

Alberta Premier Rachel Notley, who is chairing the meetings, said Wednesday's hearings will be dominated by discussions around justice issues, including regulations on the legalization of cannabis.

Alberta and other provinces have launched consultations with the public and stakeholders to develop rules around age of access, where it can be sold and how to protect public safety. And Notley did not rule out asking the federal government to put the brakes on its plan for legalization to be in force by July 2018.

Race for pot regulations

"It is a very big job," Notley said. "We've told the federal government we will do everything we can to be ready but that we are not promising that it will happen and that they won't at some point receive a request from us to slow it down a bit."

David Taylor, spokesman for Justice Minister Jody Wilson-Raybould, said it remains the government's intention to have the new laws in place no later than July 2018. In provinces or territories that have not yet authorized retailers, adults will be able to buy cannabis directly from a federally licensed producer by ordering online, with secure home mail delivery, he told CBC News.

This week's meetings will take place without one key premier at the table.

John Horgan will be sworn in as B.C.'s NDP premier on Tuesday. (Rafferty Baker/CBC)

John Horgan, who will be sworn in as B.C.'s NDP premier on Tuesday, said he's too busy with the transition and the wildfire crisis to attend.

Last week, he denied he was sidestepping a potentially uncomfortable confrontation with Notley over the Kinder Morgan pipeline.

Pipeline politics

"There's more than enough for me to do here, and I'm confident that anything that comes from the conference in Edmonton will be ably managed by staff," he said. "And if there's anything beyond that, I'm happy to engage in direct conversations with other premiers."

Horgan said he has been speaking with Notley about the Alberta-to-B.C. pipeline for months, but wants to have proper briefings from government officials before further discussions.

He has vowed to stop the expansion of the Trans Mountain pipeline, a project considered crucial for revitalizing Alberta's oilsands.

Errol Mendes, a constitutional expert at the University of Ottawa, said there is a "paradox" right now in provincial-federal relations, with the provinces working toward a unified approach to NAFTA while disputes over pipelines, carbon pricing and health deals continue to simmer.

"If the feds win in court on the right to implement carbon pricing and also push through the Kinder Morgan pipeline with its powers over federal undertakings, it shifts the balance significantly to the federal government in the longer term and could extend to other areas," he said.

"The Council of the Federation will be facing paradoxical forces — one set that strongly pulls the provinces together while separate forces will be pulling them apart. We live in interesting times for the council."

Separate health care deals negotiated by the federal government instead of a single collective agreement could add to the fractured relations, he said.