Iran repressed freedoms and rights for its people last year, the United States said Thursday, adding that there has been no "meaningful improvement" since President Hassan Rouhani was elected in 2013.
"Iran continued to severely restrict civil liberties, including the freedoms of assembly, speech, religion, and press, and to execute citizens at the second highest rate in the world," the US said in its annual human rights report.
On the eve of new high-level Iran-US talks on a nuclear deal, the lengthy section on Iran listed a catalogue of abuses such as "disappearances, cruel, inhuman or degrading treatment" as well as "politically motivated violence and repression."
Assistant Secretary for human rights Tom Malinowski said the United States has "not seen any meaningful improvement in the situation in Iran" since Rouhani took office in 2013.
But he stressed when asked about the nuclear negotiations with Iran, that "engagement is not the same thing as endorsement."
The purpose of the talks, which resume in Vienna over the weekend, "is not to deal with human rights issues," he insisted.
Secretary of State John Kerry is to leave Friday for the Austrian capital where he is due to meet with his Iranian counterpart Mohammad Javad Zarif for a final push to seal a deal putting a nuclear bomb out of Tehran's reach.
Three American citizens remain in jail in Iran and one is missing, despite persistent US calls for them to be released.
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The family of one of the prisoners, former Marine Amir Hekmati is planning to travel to Vienna this week hoping to press for his release.
The health of his father, who is terminally ill with brain cancer, "has worsened and his situation is dire. He desperately wants to see his son once more," the family said in a statement sent to AFP.
"Amir's family has assiduously avoided linking Amir to the nuclear talks, and does not want to insert him now," the statement said.
"They do, however, want their innocent son home."
Hekmati has now served more than three years in the notorious Evin prison, and according to the family is now eligible under Iranian law to be released.
Arrested in August 2011 during a visit to his grandmother in Tehran, Iranian authorities convicted Hekmati of spying for America's Central Intelligence Agency.
He was initially sentenced to death in 2012 but Iran's top court subsequently reduced the penalty to 10 years in prison.
The others being held are Saeed Abedini, a Christian pastor, and Washington Post journalist Jason Rezaian. Robert Levinson, a retired FBI agent, disappeared in Iran in 2007. If he's a captive, as the United States believes, he would now have been held longer than any other American.