The US measures came as Venezuela's opposition began a two-day nationwide strike
Venezuelan President Nicolas Maduro branded US sanctions leveled at his regime on Wednesday as "insolent," as pressure piled up on him abroad and at home over his controversial plan to elect a new body to rewrite the constitution.
The US measures came as Venezuela's opposition began a two-day nationwide strike aimed at ousting the president through early elections.
The deadliness of four months of violent anti-Maduro protests was further confirmed with the death by gunfire of a 30-year-old man in a demonstration in the west of the country. That was the latest in a death toll that has now hit 104.
In Washington, the US Treasury unveiled a list of 13 current and former officials, including the interior minister, senior military brass, the president of the electoral council, and the finance chief of state oil company PDVSA, whose US assets would be frozen.
The opposition and US moves are to force Maduro to give up his plan to have a 545-member "Constituent Assembly" elected on Sunday.
Critics say the body is a step towards a dictatorship, by bypassing or dissolving the opposition-held National Assembly.
Maduro called the US punishment "illegal, insolent and unprecedented."
"Who do these imperialists in the United States think they are? The government of the world?" he said in a speech.
But in his country, where there are widespread shortages of basic goods and soaring inflation, protesters are showing their discontent with Maduro's leadership. Organizers claimed 92-percent support for the walkout.
"No more dictatorship!" read signs on road barricades in eastern Caracas.
Maduro accuses the US of fomenting the unrest against him and his government, with the help of the conservative opposition.
The Venezuelan military has declared its loyalty to him.
But some 70 percent of Venezuelans are opposed to the Constituent Assembly, according to polling firm Datanalisis.
The hardening political struggle has deepened fears that months of street violence could worsen.
The opposition has planned another major demonstration in the capital on Friday.
Thousands of Venezuelans loaded with heavy bags have crossed the border into Colombia this week, fleeing the unrest.
"The elections are on Sunday and we really don't know what will happen," said one, Maria de los Angeles Pichardo, who left with her husband and son. "To be safe, we prefer to cross."
Ordinary Venezuelans remaining in their country believe ousting Maduro is their only hope for survival.
"We keep getting worse and worse off, with long lines and shortages. I think I'll strike for 48 hours," said one Caracas resident, Maria Auxiliadora.
Prominent opposition leader Leopoldo Lopez made a direct appeal to the military early Wednesday to withdraw its support from Maduro's plan, which he called a "constitutional fraud" aimed at eliminating democratic rule.
In announcing the US sanctions, Treasury Secretary Steven Mnuchin said America was "standing by the Venezuelan people in their quest to restore their country to a full and prosperous democracy."
He warned that anybody elected to the Constituent Assembly could also be slapped with US sanctions.
Thirteen countries in the 35-member Organization of American States, a regional political bloc, urged Maduro to suspend Sunday's election.
Nations including Argentina, Brazil, Mexico, the United States and Canada said the vote amounted to a "dismantling of democratic institutionality."
Venezuela's opposition, bolstered by an unofficial vote on July 16 that saw a third of the electorate reject Maduro's plan, has called for a boycott of Sunday's vote.
The president's attorney general, Luisa Ortega, has also broken ranks with the government over the issue and become a vociferous opponent.
At the same time, Maduro's administration is being squeezed by a long-running economic crisis.
The oil export-dependent economy will shrink 12 percent this year, after a contraction of 18 percent last year, according to the latest forecast from the International Monetary Fund.
Inflation is projected to top 720 percent.
Venezuela's currency reserves have dwindled to under $10 billion as the government keeps up debt repayments at the expense of imports to stave off a crippling default.
The opposition-led National Assembly, meanwhile, has challenged the government by appointing 33 supreme court judges to rival ones loyal to Maduro.
Three of the "shadow" judges have been arrested in the past few days by Venezuelan intelligence officials.
Adding to Venezuela's isolation, a major Latin American airline, Avianca of Colombia, said it would stop flights to and from Venezuela in mid-August.
Several other airlines have previously announced flight suspensions as currency controls imposed by Maduro's government have kept them from recovering costs or making a profit.