MEXICO CITY, April 6 (Reuters) - Mexico’s Petroleos Mexicanos expects to maintain financial debt of $105 billion between 2021 and 2025 and increase crude refining, the state oil company said on Tuesday. Pemex, as the company is known, said one of its priorities will be to free up funds and gradually pay back some of its debt without necessarily taking on new obligations. “It is clear that high indebtedness represents a structural problem, attention to which should not be delayed,” Pemex said in its latest business plan. “In the medium term, we do not rule out restructuring.” Ratings agencies stripped Pemex of its coveted investment grade rating last year because of its high debt and other concerns. Pemex also said it expects crude refining to be 1.1 million barrels per day this year and rise to 1.6 million barrels per day in 2025. (Reporting by Ana Isabel Martinez and Adriana Barrera; editing by Cassandra Garrison and Emelia Sithole-Matarise)