After the ice broke up and the ferry began running on the Liard River, two rangy Indians with weathered faces and easy gaits shouldered a sack of beaver and muskrat pelts for the spring fur auction and took a rifle for bear protection.

On their short hike through the woods to the ferry landing, Jonas and Roy Mouse paused as they often do, heads bowed and caps in hand, at a rosary-draped cross that marks the spot where their aged mother collapsed and died several years ago. The cross stands alongside an oil pipeline that was dug through their forested homeland and that the brothers say for eight years drove away animals that they hunt and trap for a living.

Today, the brothers, members of the Dehcho First Nations, are facing another encroachment on their aboriginal way of life: an even bigger 800-mile-long natural gas pipeline that would bisect the tribe's traditional territory and help spawn industrial development in Canada's vast boreal forest, one of the last intact stretches of the Earth's original forest cover.

For three decades, the Dehcho have been resisting the $7-billion project, which is backed by other native groups in the Northwest Territories. But the Dehcho are under mounting pressure to drop their opposition to a project that would serve North American energy markets as the United States strives to reduce dependence on the Middle East. Canada is already the largest foreign supplier of natural gas to the U.S.

The companies that want to build the underground pipeline — Imperial Oil, Shell Canada, ConocoPhillips and ExxonMobil Canada — estimate that it would carry 1.2 billion cubic feet of gas per day, which industry experts say is enough annually to heat more than 3 million homes for a year.

Recently, officials of Canada's newly elected Conservative government signaled their unwillingness to let the Dehcho stand in the way of the project, which proponents want to start building in 2008 and finish a few years later. Jim Prentice, minister of Indian affairs, declared that the pipeline, which still needs regulatory approval, would be built along the Mackenzie Valley with or without the tribe's blessing.

However, Prentice's remarks only stiffened resistance from the 4,500-member tribe, the largest native group along the pipeline and the only one with an unresolved claim to its traditional lands.

Grand Chief Herb Norwegian said that if the government tried to expropriate Dehcho land for pipeline construction, the tribe would retaliate with litigation and possibly blockades.

"People think of a pipeline like a garden hose in your yard," Norwegian said. "But a pipeline of this magnitude is like building a China Wall right down the valley, and the effects will be there forever and ever."

Many Dehcho fear that hundreds of trucks would disrupt their quiet communities, that construction camps would breed drug and alcohol abuse, and that the massive project would drive away caribou, moose and other wildlife that sustain people like the Mouse brothers.

In the long run, they fear the project would spur a wave of oil and gas prospecting that would bring more pipelines and roads and so many newcomers that the Dehcho could become a powerless minority in the land they have occupied for many centuries.

The pipeline would tap into 6 trillion cubic feet of natural gas in three well fields north of the Arctic Circle. It would move the gas south along the Mackenzie River to Alberta province, where it would be used to fuel a massive oil extraction project or be sent directly to markets in Canada and the United States.

"It is a significant new supply source," said Imperial Oil spokesman Pius Rolheiser. One trillion cubic feet could serve all of Canada's gas-heated homes for a year, he said.

The project is expected to spur development of other natural resources in the Territories, an area that is almost three times larger than California but has only 42,000 inhabitants.

"You are going to get a lot of lateral pipelines built into the system," said Chris Theal, research director at Tristone Capital Inc., a worldwide energy investment bank.

But about 40% of the pipeline route crosses land claimed by the Dehcho, and before approving the project, they want a power-sharing agreement over 80,000 square miles of ancestral territory, allowing them to preserve lands for cultural or environmental reasons, to control industrial development and to collect royalties and taxes.

Dehcho leaders acknowledge that withholding support for such a significant project gives them leverage to secure unprecedented authority.

Government officials say their demands are unrealistic. "It would give 4,500 people the power to govern an area about half the size of France," said Tim Christian, the chief federal negotiator. "And we certainly have not done that anywhere else [in Canada] and do not believe that is an appropriate model."

The government recently offered the Indians $104 million and ownership of about 18% of their traditional land, but Norwegian called it a "low-ball" offer.