State-run firm PDVSA faces around $5.2 billion in payments to bondholders in 2016, much of it in October and November, a sum that some experts say it will be hard-pressed to meet after the government used nearly all of its available cash reserves to pay $1.5 billion in maturities last week.

A default could curtail some of the OPEC member's exports by crippling its ability to import crude and fuels used to blend its extra heavy oil, experts and sources say. It could also degrade the quality of domestic gasoline by limiting purchases of necessary components.

With the risk growing and payment delays to suppliers already emerging, some firms that sell to PDVSA have begun hedging their bets by using intermediaries or seeking higher prices, fearful they might never get paid, according to sources who deal with the firm.