A campaign to gain UNESCO World Heritage Site status for a large swath of boreal forest along the Manitoba-Ontario border hit a major setback.

The area known as Pimachiowin Aki, which includes several Manitoba and Ontario First Nations in the region, covers 33,400 square kilometres.

READ MORE: Huge forest along Manitoba-Ontario border moves closer to UNESCO recognition

It was slated to be included in this this year’s UNESCO World Heritage Committee’s nominations currently happening in Istanbul, Turkey.

Pikangikum First Nation, which had pledged support for the project, withdrew its support in early June. On Sunday, a corporation made up of several First Nations in the bid for recognition said the nomination had been “referred” after Pikangikum -- in northwestern Ontario -- announced it would no longer support the bid.

In a phone call with CTV News Pikangikum First Nation Chief Dean Owen said he was busy and declined to comment Sunday.

“We are all very disappointed that we encountered these challenges at such a critical time in the nomination process, after working on this project for 12 years," William Young -- Pimachiowin Aki Corporation board member and spokesperson from Bloodvein River First Nation in Manitoba -- said in a news release.  

"After considerable discussion with all parties involved, we felt that we had no option but to seek a referral to give us all a chance to regroup and consider potential options for proceeding with the project."

“The Committee’s referral process allows up to three years for the submission of additional information for the World Heritage Committee to consider,” the Pimachiowin Aki Corporation said in the release.

Pikangikum withdrew its support because of "about errors in the UNESCO evaluation reports," the corporation said in the news release. The corporation said it submitted corrections along with Parks Canada, and UNESCO produced revised documents.

“We were very disappointed,” said Pimachiowin Aki project manager Gord Jones.

The Manitoba NDP says the designation would bring major economic and cultural opportunities to the province, and allow first nations to share their stories with the world.

“It's definitely a setback but it doesn't mean the bid is dead,” said environment critic Rob Altemeyer.

"The tourism potential of a UNESCO world heritage site designation is enormous. That's one of the reasons we were interested and more importantly is why the first nations were interested," he said.

Pimachiowin Aki has up to three years to take the corrections back to the first nations for review. if everyone agrees, the bid could be back in front of UNESCO decision makers next summer.

The previous NDP government had worked for years to obtain UNESCO recognition for the area and chose the current proposed route for the Bipole III Hydro transmission line down the west side of Lake Winnipeg largely because of it.

In June, Premier Brian Pallister said he may reconsider the proposed route. He said if Manitoba Hydro wants to build the line down the east side of Lake Winnipeg, he would discuss the matter with the First Nations and make the decision that is “in the best interests of Manitobans.”

READ MORE: Manitoba premier may consider relocating hydro line to First Nations area

Pimachiowin Aki Corporation said the Bipole III review was addressed in a letter the Canadian government submitted to the World Heritage Centre. The information from that review could be factored into any future resubmission of the nomination, it said.

In a statement to CTV News, Minister of Sustainable Development Cathy Cox said:

"The UNESCO bid has been referred because of concerns raised by a reserve located in Ontario based on wording in the application relating to their treaty rights. As we have to this point, we will continue to work with Federal, Provincial, Municipal & First Nations groups on the UNESCO application process."

The corporation said it will continue internal discussions over the issues raised by Pikangikum and get advice from Parks Canada and the UNESCO Advisory Bodies on next steps.

- With files from The Canadian Press and Beth Macdonell