Iran on Tuesday "strongly" condemned the decision by the outgoing administration of US President Donald Trump to return Cuba to the country's blacklist of state sponsors of terrorism.

US Secretary of State Mike Pompeo announced the designation on Monday, undoing then-president Barack Obama's 2015 move to delist Cuba as a state sponsor of terrorism in a bid to improve ties.

"With this action, we will once again hold Cuba's government accountable and send a clear message: the Castro regime must end its support for international terrorism and subversion of US justice," Pompeo said in a statement, referring to former leaders Fidel and Raul Castro.

Iran's foreign ministry spokesman Said Khatibzadeh described Pompeo's statement as "another baseless American allegation", condemning officials of the "terrorist regime" in Washington for their "repugnant habit of making false accusations". 

Trump has reversed many of Obama's efforts to normalise relations with Cuba, also ramping up sanctions against the Havana government.

Since the Iranian revolution of 1979 that overthrew the pro-American regime of Shah Mohammad Reza Pahlavi, Iran and Cuba have regularly given each other diplomatic support, with the Islamic Republic condemning the US embargo against Cuba and Havana advocating Iran's right to civilian nuclear power.