CHEYENNE, Wyo. — Two pipeline companies have unveiled plans to construct an 800-mile pipeline that would transport natural gas from Wyoming to Canada and U.S. markets in the Midwest and Northeast.

Alliance Pipeline Inc. and Questar Overthrust Pipeline Company said the 42-inch Rockies Alliance Pipeline would start at Wamsutter in south-central Wyoming and traverse Wyoming, Montana and North Dakota en route to a trading hub on the Minnesota-Canada border.

The project, estimated to cost $3.5 billion, would connect with other lines to ship gas to midwestern hubs and storage facilities, including sites in Chicago and Michigan, officials said.

The companies touted the project's ability to connect the Rocky Mountain region — the nation's fastest-growing natural gas producer — and hungry markets in the United States and central Canada.

The Rocky Mountain gas industry has been ramping up pipeline construction to maximize profits of the region's plentiful supply.

Alliance and Questar will start taking bids May 1 from customers who want to use the pipeline.

The companies are targeting the fall of 2011 for opening the entire length of the pipeline, pending financing and regulatory approval.