EDMONTON -- Alberta says it will take action on two fronts Thursday in its escalating fight with Saskatchewan over the ban on Alberta licence plates on Saskatchewan job sites.

Deron Bilous, Alberta's economic development minister, said unless Saskatchewan relents he will launch a formal application under the New West Partnership.

He said Saskatchewan's licence plate ban is a clear violation of the agreement that calls for a barrier-free interprovincial market between the four western provinces.

"They have until midnight tonight to smarten up, come to their senses and walk this back or we will be filing a trade injunction," Bilous said Wednesday.

Bilous has previously suggested there would be other retaliatory measures and said details on those would be addressed Thursday.

Last week, Saskatchewan Premier Brad Wall's government announced it would ban vehicles with Alberta licence plates on any future Saskatchewan government road and building construction sites.

It has given multiple reasons for the ban.

Last week, Saskatchewan Infrastructure David Marit said the reason was because Alberta had similar rules for Saskatchewan workers. Bilous said those rules don't exist.

Marit also said it was because Alberta doesn't have a provincial sales tax, and that making Alberta workers buy Saskatchewan plates puts workers in both provinces on a level playing field.

Wall himself suggested it was payback after Alberta changed rules on craft beer taxes to help its own industry and lobbied against open borders on procurement.

Bilous said he spoke on Tuesday with Marit and Saskatchewan Trade Minister Steven Bonk but they could not provide a credible rationale for the ban.

"They were all over the map as far as the reasons behind doing this, citing Alberta not having a PST," said Bilous.

"They listed a couple of other examples, but weren't able to provide any concrete examples of Alberta contractors or Alberta tenders forcing Saskatchewan contractors to change their plates."

Bonk said they have anecdotal evidence.

"We're hearing loud and clear from the Saskatchewan Heavy Construction Association as well as some of our contractors that this is a real issue for them," said Bonk.

"This is a measure to protect Saskatchewan companies. We just want to level the playing field."

Bonk said he was a bit taken aback that Alberta was moving ahead with the formal protest under the New West Partnership after the talk with Bilous.

"I thought we had quite a productive conversation," said Bonk.

"We're a little bit surprised by that because when we left the call yesterday we were under the impression that we agreed to meet in the new year, in January, to discuss this further."

Bilous also accused Saskatchewan of applying the licence plate ban to not only new contracts as promised, but also to existing ones.

Bonk said that is not the case.

Service Alberta, the department that handles licences, says a non-resident needs to register a vehicle if it is in Alberta for six months or more. However, commercial vehicles and trucks are not included in the requirement.