Venezuela showed new signs of a financial unraveling on Friday, as the state electricity company was declared in default.

The announcement of the country’s first bond default came three days before the government was to begin talks with investors to refinance and restructure more than half of its $120 billion in debt.

“This is the first drizzle in a huge thunderstorm,” said Jose L. Valera, an international energy lawyer in the Houston office of the Mayer Brown law firm. “The whole country of Venezuela is bankrupt.”

The electricity company, Corpoelec, based in Caracas, was unable to make a $28 million payment on a $650 million bond. The bond was originally issued by Electricidad de Caracas before it was nationalized as a Corpoelec subsidiary a decade ago.

The default was announced in a notice by Wilmington Trust after bondholders complained that they had not received payment on a coupon that was due on Oct. 10 but had a grace period that ended on Thursday.

Venezuela and its state-owned enterprises — including the oil company Petróleos de Venezuela, known as Pdvsa — have missed roughly $350 million in interest payments over the last month. The grace period on many of them will end in the next few days.

“There are going to be so many different debtors from the sovereign to these different state-owned companies,” Mr. Valera said, “and they are all going to be defaulting at the same time.”

President Nicolás Maduro announced last week that the government would refinance and restructure $63 billion in bonds, and invited investors to meet with a government committee led by his vice president. It is uncertain how many investors will take part, since United States sanctions restrict any negotiation or purchases of new bonds by American-regulated financial institutions.

Monday could be a decisive day in Venezuela’s credit crisis.

While President Maduro’s committee will offer restructuring proposals, the International Swaps and Derivatives Association, a panel formed by the derivatives industry, will meet to discuss the Venezuelan debt situation.

The panel will discuss whether late and partial payments of $1.2 billion due last week from Pdvsa constituted a “credit event” that could prompt bondholders to organize to seek payment. The creditors could pursue legal action to confiscate Venezuelan assets abroad, such as oil tankers or even refineries owned by the Pdvsa subsidiary Citgo.