Standard & Poor's declared Venezuela in "selective default" on Monday, after it failed to make $200 million in payments on its global bonds, becoming the first credit ratings agency to do so.
The agency said it acted after a 30-day grace period had passed on payments on two bonds.
"We have lowered two issue ratings to 'D' (default), and we lowered the long-term foreign currency sovereign credit rating to 'SD' (selective default)," the agency said.
S&P's verdict came after the Venezuelan government met with international creditors in Caracas but offered no concrete plan for restructuring its $150 billion debt.
Participants at the meeting told AFP that officials said the government intended to form working groups to evaluate short- and mid-term debt renegotiation proposals, but gave no specifics.
"We would very likely consider any Venezuelan restructuring to be a distressed debt exchange and equivalent to default given the highly constrained external liquidity," S&P said.
"In addition, in our opinion, US sanctions on Venezuela and government members will most likely result in a long and difficult negotiation with bondholders," it said.
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.
Ratings on those bonds also will be lowered to "D," of default, if not paid on time, it said.
The unpaid obligations total $420 million, the agency said.