MEXICO CITY, July 22 (Reuters) - Mexico's Finance

Ministry announced an upcoming operation on Tuesday aimed at

strengthening the finances of the country's heavily-indebted

state energy company Petroleos Mexicanos (Pemex).

In a statement, the ministry said the operation would

consist of issuing financing instruments called Pre-Capitalized

Notes, but that the operation would not constitute a guarantee

for the company.

The ministry's statement did not say how much the sale aimed

at raising for Pemex.

Earlier on Tuesday, Bloomberg News reported, citing

unnamed sources, that the government was looking to raise

between $7 billion and $10 billion with the sale.

Pemex, the world's most indebted energy company, has an

outstanding debt with an extensive list of suppliers and

contractors of around $20 billion, in addition to another

financial debt of $101 billion, despite the injection of

billions of dollars from the government in the last few years to

face the amortizations.