Liz Truss will meet the Iranian foreign minister to call for the immediate release of UK nationals such as Nazanin Zaghari-Ratcliffe, who are being detained in Iran.
The new Foreign Secretary will speak to Hossein Amir-Abdollahian, along with a number of her international counterparts, for the first time at the United Nations General Assembly in New York on Monday.
Among the discussions will be UK nationals trapped in Iran, such as Ms Zaghari-Ratcliffe, Anoosheh Ashoori and Morad Tahbaz.
She will also call on the country to comply with its nuclear commitments.
Ms Truss said: “I will be asking Iran to ensure the immediate and permanent release of all arbitrarily detained British nationals in Iran, and to begin working with us to mend our fractured relations.
“The UK, US and our international partners are fully committed to a nuclear deal, but every day that Iran continues to delay talks whilst escalating its own nuclear programme means there is less space for diplomacy.”
Mr Ratcliffe said on Sunday that he had given Ms Truss the names of 10 people he accuses of being involved with “hostage-taking” in Iran.
His wife, a British-Iranian dual national, has been in custody in the country since 2016 after being accused of plotting to overthrow the government.
“Partly I just want to hear that this is a top priority and that Nazanin and the others who are being held as bargaining chips will be brought home.
“This coming week she (Ms Truss) should be meeting with the new Iranian foreign minister in New York when they’re over for the UN event, so hopefully there will be a positive conversation.
“Right now I think enough needs to be enough, and it needs to be signalled really clearly to Iran that you can’t use innocent people in this way.
“I’d really like them to be firm, to be brave and make some clear steps.”
Sacha Deshmukh, chief executive of Amnesty International UK, said: “One of the things we’d like to see most urgently from the new Foreign Secretary is a clearly articulated strategy for securing the release of British nationals arbitrarily detained in Iran.
“The plight of Nazanin Zaghari-Ratcliffe, Anoosheh Ashoori and other UK nationals held in Iran has extended across the last four foreign secretaries – it’s long past time that the UK finally brought this deeply distressing episode to an end.”