The approval, which follows an investigation of the company’s proposal announced in March 2016, also satisfies one of the conditions required to complete the deal.

The transaction is due to receive an approval from the US Federal Trade Commission (FTC) under the Hart-Scott-Rodino Anti-Trust Improvements Act (HSR Act), as well as Columbia’s stockholders.

Columbia Pipeline currently owns and operates about 15,000 miles of natural gas pipelines which connect the US Gulf Coast to the Midwest, Mid-Atlantic and Northeast US.

TransCanada and Columbia expect to complete the deal later this year.

The deal is a part of TransCanada’s effort to strengthen its natural gas transmission business.

TransCanada expects the deal to create one of the North America’s largest regulated natural gas transmission businesses with a combined $23bn portfolio of secured, near-term growth projects.

Upon completion of the deal, Columbia will cease to be a publicly held corporation and will become an indirect wholly-owned subsidiary of TransCanada.

Additionally, TransCanada will own the general partner of Columbia Pipeline Partners LP, which will remain a publicly traded partnership.

TransCanada operates a network of natural gas pipelines that extends over 66,400kmand taps major gas supply basins in North America.