Canada's largest forestry companies and environmental groups have declared peace on the management of the country's massive northern forest, sources say.

An agreement to be made public Tuesday involves 21 of Canada's biggest logging companies and nine environmental organizations that in the past have been among the most critical of Canadian forestry practices.

A sawmill in Grand Forks, B.C., in 2007. The agreement is said to cover the most sensitive parts of the boreal forest in B.C., Alberta and Quebec. (Jeff Bassett/Canadian Press)

The formal announcement is to be made in Toronto on Tuesday.

The Forest Products Association of Canada refused to release details Monday, but sources say it involves protection of some of the most sensitive parts of the country's boreal forest in B.C., Alberta and Quebec.

Some environmental groups were enthusiastic about how the agreement would work in protecting the boreal forest, which comprises about 77 per cent of Canada's woodland area.

The boreal forest stretches like a green ribbon from the Yukon to Newfoundland and is home to two-thirds of the country's estimated 140,000 species of plants, animals, and microorganisms.

Among the forestry companies involved in the deal are Canfor, AbitibiBowater, Tembec, West Fraser and privately owned Kruger.