Investors and ratings agencies have criticized the project over concerns that it would divert funds away from Mexican state oil company Pemex's more profitable exploration and production business.

"This government will build it," Nahle said in a radio interview. "Why would we backtrack on that? It is a viable project, it's a necessary project, it's a Pemex project."

The refinery in President Andres Manuel Lopez Obrador's home state of Tabasco was a signature campaign promise of the left-leaning energy nationalist. Lopez Obrador has said the refinery  would help Mexico wean itself off its growing reliance on fuel imports, the vast majority of which come from US refiners.