The United States has declared Venezuela's consul general in Miami persona non grata and said she must leave the country by Tuesday.
The diplomat, Livia Acosta Noguera, is alleged to have discussed possible cyber-attacks on the US while based at the Venezuelan embassy in Mexico in 2008.
The FBI has been investigating the comments, AP news agency says.
The US state department did not comment on the reason for the expulsion.
A spokesman said the decision was taken in accordance with Article 23 of the Vienna Convention on Consular Relations.
Four US members of Congress had written to the US Secretary of State Hillary Clinton in December raising concerns about the diplomat.
The letter said that according to a documentary broadcast on the Spanish-language network Univision last month, Ms Acosta Noguera had discussed attacking the US government's computer systems with diplomats from the Iranian and Cuban embassies and students posing as extremists, while she was vice secretary at Caracas's embassy in Mexico.
The congressmen asked the state department to investigate the claims, and if it found them to be true, "declare her a persona non grata and require her immediate departure from the United States".
Venezuelan President Hugo Chavez made no reference to the expulsion in his weekly broadcast, Alo Presidente, which resumed after a seven-month pause during which he underwent treatment for cancer.
However he did accuse Washington of "inventing" plots by Iran to attack the US with help from Cuba, Nicaragua and Venezuela.
Iranian President Mahmoud Ahmadinejad arrived in Venezuela on Sunday for his fifth visit to the country, at the start of a week-long trip to Latin America.