Chief Sandford Big Plume, seen in July, said the Tsuu T'ina were not properly consulted on road work at 37th Street and Glenmore Trail. (CBC)

A war of words between Calgary's mayor and the chief of the Tsuu T'ina First Nation about a traffic circle, related to the southwest ring road, has the leaders calling each other's actions "unreasonable" and "aggressive."

Mayor Dave Bronconnier publicly released letters between the band and the city this week, which outline the band's position that it was not properly consulted on the traffic circle on 37th Street and Glenmore Trail S.W.

"Any time I read a letter that threatens not only legal action, but demands meetings and demands a halt to construction to work within the City of Calgary boundaries by an adjacent municipality, I think that's aggressive," said Bronconnier on Monday.

The city built the traffic circle to improve traffic flow on Glenmore Trail; the road to the Tsuu T'ina's casino also connects to the same roundabout.

'I simply believe that city leadership is being unreasonable by threatening to block both access and development to our nation.'—Chief Sandford Big Plume

Big Plume's letter requests that the city halt further road work, including a major interchange at that intersection, which the band considers a threat to their members' access.

"Any interference by the City of Calgary of Tsuu T'ina Nation's rights to enter and leave its lands at any point along Tsuu T'ina boundaries constitutes a breach of our rights under Treaty No. 7," Chief Sandford Big Plume wrote on Oct. 2 in the letter also sent to federal and provincial ministers.

Big Plume goes on to threaten legal action if the band did not receive an immediate response.

"Those letters are very clear. They're looking for effectively a veto over building this interchange and that's not the approach that we take," said Bronconnier.

Calgary Mayor Dave Bronconnier said the plans for an interchange are going ahead. (CBC)

In a June referendum, Tsuu T'ina members rejected a deal to sell their land to the province to build the southwest portion of Calgary's ring road. The rebuff ended decades of negotiations and forced the provincial government back to the drawing board.

In a statement released on Monday, Big Plume said, "The Tsuu T'ina have no interest in or desire to prevent transportation development in the City of Calgary, I simply believe that city leadership is being unreasonable by threatening to block both access and development to our nation."

Bronconnier said the city has never threatened to block the band's access. He said the 37th Street access point has always been "considered temporary," and pointed out the band's legal access is at Anderson Road.

The mayor said the city has no plans to abandon the interchange.

Tom Flanagan, a political scientist at the University of Calgary and an expert on native rights and land claims, said while the city isn't breaking any specific clause, it could be violating the spirit of Treaty 7.

"I think access is probably implied in the treaty because it sets access for Indians to live on, so it wouldn't be viable for them to get in and out, so I think the courts would find there is a requirement there for reasonable access," said Flanagan.