Venezuela is buried under a $150 billion foreign debt mountain, including $28 billion owed to its biggest creditor China and another $8 billion to Russian Federation.
Venezuela hosted a brief meeting with creditors in Caracas on Monday to discuss its total $150 billion foreign debt but the discussions ended without any agreement.
S&P said there was "a one-in-two chance that Venezuela could default again within the next three months".
Besides the two bond payments it has defaulted on, Venezuela is overdue on four other debt payments but they were still within the 30 day grace period, S&P said.
There's still hope for restructuring with only some issues in peril.
"If any potential restructuring operation is completed, we would lower all of our foreign currency ratings on Venezuela to default and subsequently raise them to the "CCC" or "B" category".
In the case of Venezuela, the government of President Nicolás Maduro failed to make $200m in payments on two global bond issues by 12 November, when a 30-day grace period expired.
Mr Aissami, who has been accused of drug trafficking by the United States, is himself on the list of Venezuelan individuals sanctioned by the U.S. treasury department.
Participants at the meeting told AFP that officials said the government meant to form working groups to evaluate short- and mid-term debt renegotiation proposals, but gave no specifics.
Adding to the pressure on Maduro was the European Union's announcement of sanctions.
The US called an informal meeting of the UN Security Council, where US Ambassador Nikki Haley slammed Venezuela as an "increasingly violent narco-state" that poses a threat to world security.
Venezuela's envoy to the UN, Rafael Ramirez, called the meeting "illegal" and a "hostile" act "of interference" by the US.