Washington officials say they won't renew a license due to expire early Thursday, which had broadly eased restrictions.
Hours before the deadline, the U.S. Treasury Department issued a new license, giving firms 45 days to wind down oil and gas operations in the country.
It all comes after Venezuela President Nicolas Maduro failed to honor all terms in the deal that had eased sanctions.
The U.S. says he's breached a promise to allow the opposition to run the candidate of its choice in July's presidential election.
However, the news of renewed sanctions drew a defiant response from the Venezuelan leader:
"When did we become a gringo colony? A star of the United States? When? Can someone tell me? Venezuela is a country that walks on its own feet, uses its own head, produces with its own hands."
Government supporters insist Venezuela has honored the deal with the U.S.
But Washington says Maduro has harassed, intimidated or detained opponents.
Multiple opposition allies and activists have faced arrest in recent months.
Opposition leader Maria Corina Machado condemned the government's actions:
"The regime violated every agreement; they haven't complied with everything they promised. Instead, they've intensified repression, they've incarcerated more people, they've persecuted, they've barred opposition members: everything they said they wouldn't do."
Global oil prices rose following news of the new sanctions.
International benchmark Brent crude gained around a quarter of a percent early Thursday.
Prices had already faced upward pressure amid concern conflict in the middle east could affect supplies.
