The companies proposing a major pipeline to move natural gas from Alaska to the Lower 48 estimate the project will cost from $20 billion to as much as $41 billion, depending on the route.

The Alaska Pipeline Project details came Friday in a filing with federal regulators. The filing is a first step toward an open season, when the companies behind the project will try to ink shipping deals with North Slope gas producers.

TransCanada Corp. is working with Exxon Mobil Corp. to advance the pipeline. The state of Alaska has promised to reimburse TransCanada up to $500 million of the cost.

Early cost estimates from a few years ago were about $26 billion.

A rival project by BP PLC and ConocoPhillips is also moving ahead.