The Canadian firm has to sell its stake in Chile's SQM to be able move ahead with a merger with fertilizer firm Agrium.
The new regulation is part of energy ministry's RenovaBio program for the development of the biofuels industry.
The OPEC country, which relies on oil for 95% of its export earnings, has seen output halve to 1.5Mb/d since the early 2000s amid shrinking investment, corruption and crippling sanctions.
The Brazilian federal oil giant is also pushing ahead with the sale of its shares in petchem company Braskem.
Duncan Wood of the Woodrow Wilson Center discusses how the Mexican energy sector's incorporation in the renegotiation process will reflect new realities and the urgency cast over negotiations due to the possible victory of Andrés Manuel López Obrador in July's presidential elections.
Energy minister's decree came on the same day as Petrobras started the disclosure of information on its refinery divestments against a backdrop of protests by workers.