Canadian pipeline giant Enbridge announced Tuesday that it is buying three utilities from US-based Dominion Energy in a $14 billion deal that will make it North America's largest natural gas supplier.

Enbridge, which operates the world's longest petroleum pipeline system, said it is doubling its gas distribution business with the acquisitions.

The deal underscores the continued value producers are placing in natural gas even as countries strive to reduce fossil fuel dependence to curb greenhouse gas emissions.

Advocates argue natural gas is less polluting and better for the environment than coal, while critics point to its methane output.

Enbridge, which pitches itself as a leader in Canada's transition to renewable energy, called Tuesday's deal "a once in a generation opportunity."

"Today and for the long-term, natural gas will remain essential for achieving North America's energy security, affordability and sustainability goals," Enbridge CEO Greg Ebel said in a statement.

Enbridge is purchasing East Ohio Gas, Questar Gas Co and Public Service Co of North Carolina for $9.4 billion in cash plus $4.6 billion in debt assumption.

The utilities serve customers in Ohio, Utah, Wyoming and North Carolina.

Enbridge's shares fell 6.2 percent in after-hours trading overnight Tuesday.