Sempra Energy on Wednesday unveiled a plan to unify its U.S. and Mexico subsidiaries that own liquefied natural gas (LNG) assets.

The move to combine Sempra LNG and Mexican firm Infraestructura Energética Nova (IEnova) comes after the San Diego-based operator last month funded construction of the $2 billion Energia Costa Azul (ECA) LNG export terminal, their 50-50 joint venture. The export project would use U.S. feed gas and would be built at the site of the mothballed ECA LNG import terminal in Baja California, Mexico. The import terminal was built before the unconventional gas boom.

Sempra plans to acquire the 29.8% of the IEnova shares it does not own and form Sempra Infrastructure Partners. The partnership would own all of Sempra LNG and IEnova assets, spokeswoman Christina...