To provide new legal protections for the high-profile public project, Mexico's president declared on Thursday that the construction and management of a tourist train project, which might cost up to $20 billion, is a concern of national security.

The Mayan tourist train project and the transoceanic freight rail corridor are both comprised of transportation infrastructure, and President Andres Manuel Lopez Obrador invoked government and national security prerogatives over "the construction, operation, maintenance... execution and administration of the transport infrastructure" in a decree that was published in Mexico's official gazette.

These initiatives are among Lopez Obrador's most expensive infrastructure goals to boost development in Mexico's southernmost region.

The decree cited the necessity for security over the flow of commodities and persons and referred to constitutional provisions providing the state responsibility over national growth and planning

Three airports in southern Mexico's cities of Palenque, Chetumal, and Tulum received the same national security designation; these locations are close to the 1,500-km (930-mile) path of the railway and the borders with Guatemala and Belize.

The tourist railway will connect many beach resorts with ruin sites dating to the classical apex of the Maya civilization throughout five Mexican states along the Yucatan Peninsula.

Environmentalists are concerned that the $20 billion tourism project, which Lopez Obrador has estimated may cost, could threaten animals and fragile old cave systems that dot the proposed path.