The US move comes a day after it pushed for restoration of UN sanctions on Iran, including an arms embargo, arguing Tehran was in violation of a nuclear deal it struck with world powers in 2015 even though Washington itself abandoned the agreement.
The United States has imposed visa restrictions on 13 Iranian officials it accused of involvement in "gross violations of human rights" for a 1990 assassination of an Iranian opposition figure in Switzerland.
The State Department did not name the 13, but in a statement on Friday said it was also designating a 14th Iranian, Hojatollah Khodaei Souri, who it said as director of Iran's Evin Prison ran an institution "synonymous with torture and other cruel, inhuman, or degrading treatment or punishment."
"The United States will continue to pressure Iran to treat its own people with dignity and respect," US Secretary of State Mike Pompeo said.
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Today marks the annual Day of Remembrance and Tribute to the Victims of Terrorism. Terrorists must be held accountable and today we announce visa restrictions on 14 Iranian individuals for their involvement in gross violations of human rights on behalf of the Iranian regime.— Secretary Pompeo (@SecPompeo) August 21, 2020
'No one is safe'
Pompeo's statement barring the 13 officials from traveling to the United States was likely in reference to the 1990 killing of Kazem Rajavi, a leading opponent of the Iranian Government who was shot near his home in Switzerland, Reuters reported at the time, citing relatives.
Rajavi was the brother of the leader of the People's Mujahedeen, a leftist guerrilla group. The Mujahedeen's European office in Paris at the time issued a statement quoting Massoud Rajavi as saying the Iranian Embassy in Switzerland organised the killing.
Pompeo said the officials, who he called "assassins," posed as Iranian diplomats and acted "under the highest orders of their government to silence opposition and show that no one is safe from the Iranian regime."
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Tensions between Washington and Tehran have spiked since Trump unilaterally withdrew in 2018 from the Iran nuclear deal struck by his predecessor, Barack Obama, and began reimposing sanctions that had been eased under the accord.
The United States moved on Thursday to restore UN sanctions on Iran, including an arms embargo, arguing Tehran was in violation of the deal it struck with world powers in 2015 even though Washington itself abandoned the agreement.
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A 2015 Security Council resolution enshrining the nuclear deal states that if no council member has put forward a draft resolution to extend sanctions relief on Iran within 10 days of a non-compliance complaint, then the body's president shall do so within the remaining 20 days.
The United States would be able to veto this, giving it a cleaner argument that sanctions on Iran have to be reimposed.
However, the 2015 resolution also says the council would "take into account the views of the states involved." Given the strong opposition, some diplomats say the council president - Indonesia for August and Niger for September - would not have to put up a draft text.
"Faced with this very strong view of a majority of Security Council members that the snapback process has not been triggered, as the presidency they are not bound to introduce the draft resolution," said a UN Security Council diplomat, speaking on condition of anonymity.
Pompeo and the outgoing US Iran envoy Brian Hook signalled that Washington expects Indonesia or Niger to put a text to a vote. Another US option is to put forward the draft itself or ask the Dominican Republic to do so.
The United States argues that it can trigger the sanctions snapback process because the 2015 Security Council resolution still names it as a nuclear deal participant.
However, in a joint letter to the Security Council on Thursday hours after the US submitted its complaint, Britain, Germany, and France said: "Any decisions and actions which would be taken based on this procedure or on its possible outcome would also be devoid of any legal effect."
UN Secretary-General Antonio Guterres distanced himself from the showdown in the Security Council.
"Security Council members will need to interpret their own resolution," UN spokesman Stephane Dujarric told reporters. "It's not the Secretary-General."