In addition to financial debt of more than $105 billion, the company disclosed that at the end of September it owed local and foreign companies about 297 billion pesos ($17.22 billion).

Private oil operators' industry group Amexhi warned this week in a letter to the government, seen by Reuters, that Pemex's reluctance to pay threatens not only production but also projects already underway and some companies' very existence.

Addressed to Energy Minister Miguel Angel Maciel and Finance Minister Rogelio Ramirez de la O, Amexhi's letter expressed concern over what it called a "critical situation" caused by Pemex's debt.

Amexhi, which represents the interests of both local and foreign companies, asked the ministers to act.

Neither Amexhi, the finance and energy ministries nor Pemex responded to requests for comment.

Echoing these concerns was another industry group, Amespac, whose members include some of the world's largest oil service companies. This week, it asked Pemex to pay at least some of what it owed its members by Dec. 15.

"Some of the affected companies have officially notified Pemex of the impact these delays have on their financial position," the widely shared letter said, warning that not paying "will have a severe impact on hydrocarbon production in the country."

Pemex said in October that it owes Halliburton (HAL.N) the equivalent of $529 million, SLB (SLB.N) -- formerly Schlumberger -- $474 million and Baker Hughes (BKR.O) $311 million.

SLB confirmed it has been "experiencing payment delays" from its primary customer in Mexico on receivables that are not in dispute. It did not disclose the debtor's name, but added it is "adjusting activity levels with the customer on certain projects," and expects to collaboratively resolve the delays.

Halliburton and Baker Hughes did not provide immediate comment.

Under President Andres Manuel Lopez Obrador, who took office in 2018, Pemex has received the equivalent of over $70 billion in cash injections and tax breaks, plus help to pay down debt.

Pemex also disclosed invoices payable for more than 96 billion pesos in the same debt report: it owes Fieldwood Energy and its partner Petrobal about $90 million and Hokchi Energy about $127 million. Hokchi and Fieldwood, which are large local producers, both sell their output to Pemex.

The companies won oil contracts during a landmark energy reform under Lopez Obrador's predecessor Enrique Pena Nieto, who opened the industry to private investment, expertise and technology.

"Most operators have no option but Pemex," said an industry source who spoke on condition of anonymity.

In Mexico, only a few companies have permits to export production and therefore sell it to Pemex.

"If there were alternatives, it would be easy for operators to turn around and sell to other customers," the source added.

In September, Hokchi Energy said it had notified Pemex it had initiated a dispute settlement procedure because the state behemoth failed to pay $190 million for the sale of crude oil and gas.

Hokchi declined to comment further. Fieldwood Energy and Petrobal did not respond.