Calgary-based pipeline giant TransCanada says it has struck an agreement to acquire U.S. energy company Columbia Pipeline Group in a $13 billion US deal.

The deal will help expand its already vast natural gas pipeline footprint.

Columbia operates a 24,000-kilometre pipeline network that stretches from New York to the Gulf of Mexico.

TransCanada CEO Russ Girling says the deal represents a rare opportunity to snap up assets in the Marcellus and Utica shale gas regions of the northeastern U.S.

Company executives will be discussing the deal on a conference call this afternoon.

TransCanada has made headlines in recent years for its challenges in building new crude oil pipelines, like Keystone XL and Energy East.

U.S. President Barack Obama nixed Keystone XL in November following a seven-year regulatory saga.

National Energy Board hearings have not yet begun into the Alberta-to-Atlantic Energy East proposal, which has been facing mounting opposition from environmental groups and some Quebec politicians.