Pemex has hired Credit Agricole to sell its 9.3 percent stake in Repsol, Spanish online newspaper El Confidencial reported on Monday.
Pemex is a a long-time Repsol shareholder, but the relationship has become increasingly contentious.
The Mexican company has publicly fought with Repsol Chairman Antonio Brufau over his handling of negotiations after Argentina’s 2012 seizure of the company’s YPF business unit.
The YPF seizure ended in a $5 billion settlement this year.
Pemex is Repsol’s third-biggest shareholder.
The stake’s market value is worth about $3.19 billion..