MEXICO CITY, Aug 23 (Reuters) - Mexico's Pemex is the biggest liquidity and debt concern among its Latin American peers, Fitch Ratings said on Wednesday, despite billions of dollars in government support for the state energy company.

Having issued some of the world's most widely held emerging market bonds, Pemex is still popular among investors betting on unstinting support from Mexico's energy nationalist president, Andres Manuel Lopez Obrador.

The world's most indebted state energy company, Pemex has $25 billion in short-term debt and $4 billion in bonds still to mature in 2023, rating agency Fitch said in a report.

"Pemex poses the greatest maturity and liquidity concern," Fitch said, noting that as most corporate borrowers refinance shorter-term debt maturing between 2024 and 2026, it risks creating significant competition for the Mexican company.

Among its peers in the region - including Argentina's YPF, Brazil's Petrobras and Colombia's Ecopetrol - Pemex also has the highest total debt-to-proven reserves ratio at $14.70 per barrel of oil equivalent (boe), Fitch said.

Meanwhile, Pemex's lifting costs increased to $26.15 per barrel in 2022 from $19.14 per barrel a year earlier.

In 2020, Pemex became the world's largest "fallen angel": a borrower whose rating descends to junk from investment grade.

"Pemex's ratings are four notches below those of the sovereign as a result of the company's weak standalone credit profile and slow government reaction to strengthen Pemex's capital structure and ESG (environmental, social and governance) considerations," Fitch said.

Pemex did not immediately respond to a request for comment.

Last month, Pemex Chief Financial Officer Carlos Cortez told investors during an earnings call that despite government support, management was evaluating whether it would tap bond markets this year or next.

Pemex's financial debt now stands at $110 billion, mostly in bonds. Between 2019 and the end of June, Pemex received more than 730 billion pesos ($42 billion) from the government. (Reporting by Stefanie Eschenbacher; Editing by Dave Graham and Jacqueline Wong)