MEXICO CITY — Mexico’s government issued a decree Monday that will force private freight railway lines to give preference to passenger train service over their normal freight runs.

The decree gives the two main private concessionary rail operators until Jan. 15 to present proposals for offering the passenger service themselves. If they decline, the government will put the army or the navy, which have no experience operating railways, in charge of the services.

The biggest challenge could be three long passenger routes the government also wants to establish from central Mexico to the U.S. border: the 700-mile proposed passenger service from Mexico City to Nuevo Laredo, the 900-mile run from Aguascalientes to the border city of Ciudad Juarez, and the 1,350-mile route from the capital to the border city of Nogales.

The two main private freight operators in Mexico are the multinational Canadian Pacific Kansas City, known as CPKS, and Mexico’s Ferromex.