The Obama administration ordered the Venezuelan consul general in Miami expelled on Sunday.
The State Department declared the diplomat, Livia Acosta Noguera, persona non grata and gave her until Tuesday to leave the United States.
Spokesman Mark Toner said the Venezuelan government was notified of the decision on Friday, giving her 72 hours to depart under standard diplomatic procedure.
There was no immediate reaction from the Venezuelan government.
Toner would not discuss the reason for the expulsion, but said it was done in accordance with Article 23 of the Vienna Convention on Consular Relations. That article does not require the expelling state to explain its decision.
However, the move follows an FBI investigation into allegations contained in a documentary aired by the Spanish-language broadcaster Univision last month.
According to the documentary, entitled The Iranian Threat, Acosta discussed a possible cyber-attack against the US government when stationed at her country's embassy in Mexico.
The documentary was based on recordings of conversations with her and other officials, and also alleged that Cuban and Iranian diplomatic missions were involved.
The documentary, citing audio and video obtained by the students at the National Autonomous University of Mexico, Univision said Acosta was seeking information about the servers of nuclear power plants in the US.
Relations between the United States and Venezeula have been strained since the rabidly anti-American Hugo Chavez came to power in Caracas.
Chavez has proven a key ally of Iran in South America. Acosta's expulsion comes during Iranian President Mahmoud Ahmadinejad's fifth tour of South America in recent years.