Reuters

Mexico`s president said on Thursday that construction and operation of a tourist train project that could cost up to $20 billion is a matter of national security, offering new legal protections for the high-profile public work.

In a decree published in Mexico`s official gazette, President Andres Manuel Lopez Obrador invoked government and national security prerogatives over "the construction, operation, maintenance ... execution and administration of the transport infrastructure" that makes up both the Mayan tourist train project as well as the transoceanic freight rail corridor.

The projects are among Lopez Obrador`s most costly infrastructure priorities aimed at bringing more prosperity to Mexico`s poorer south.

The decree pointed to constitutional provisions giving the state control over national development and planning, citing the need for security over the movement of goods and people.

It bestowed the same national security designation on three airports in southern Mexico in the cities of Palenque, Chetumal and Tulum, near the train`s planned 1,500-km (930-mile) route and close to the country`s border with Guatemala and Belize.

Spanning five Mexican states across the Yucatan Peninsula, the tourist train will link a series of beach destinations with ruin sites dating to the Maya civilization`s classical peak.

The tourist project that Lopez Obrador has said could ultimately cost $20 billion has raised alarm bells from environmentalists, who say it could endanger wildlife and delicate ancient cave systems that dot the planned route.