The sanctions follow through on a U.S. threat to take action against Maduro and his socialist government if they went ahead with Sunday's election, which the administration decried as a “sham.”
“All options are on the table, and we will consider everything,” Treasury Secretary Steven Mnuchin told reporters at Monday’s White House briefing.
The sanctions freeze any assets Maduro may have in U.S. jurisdictions and bar Americans from doing business with him. They were outlined in a brief notice by the Treasury Department's Office of Foreign Assets Control ahead of a White House announcement.
The monetary impact of the sanctions wasn't immediately clear as Maduro's holdings in U.S. jurisdictions, if he has any, weren't publicized. However, imposing sanctions on a head of state is rare and can be symbolically powerful, leading other countries to similarly shun such a leader. For example, the U.S. has had sanctions against Syria's President Bashar Assad since 2011.
"Yesterday's illegitimate elections confirm that Maduro is a dictator who disregards the will of the Venezuelan people," Mnuchin said. "By sanctioning Maduro, the United States makes clear our opposition to the policies of his regime and our support for the people of Venezuela who seek to return their country to a full and prosperous democracy."
He warned of further U.S. penalties against Maduro allies.
"Anyone who participates in this illegitimate (constituent assembly) could be exposed to future U.S. sanctions for their role in undermining democratic processes and institutions in Venezuela," Mnuchin said.
Officials had said the sanctions could target Venezuela's oil sector, including possibly its state-owned petroleum company.
But after the announcement, an official said Trump's administration held off due to possible complications, including some involving subsidiaries. The official wasn't authorized to speak publicly on the process and demanded anonymity.
The assembly will draw up a new constitution that many believe is aimed only at securing Maduro's increasingly authoritarian rule. On Monday, Venezuela's government said the election had given it a popular mandate to dramatically recast the political system, despite widespread claims of low voter turnout.
The Trump administration was quick to denounce the vote.
"Maduro's sham election is another step toward dictatorship," Nikki Haley, the U.S. ambassador to the United Nations, said on Twitter. "We won't accept an illegit govt. The Venezuelan ppl & democracy will prevail."
State Department spokeswoman Heather Nauert said the new assembly "is designed to replace the legitimately elected National Assembly and undermine the Venezuelan people's right to self-determination."
The Associated Press contributed to this report.