British Prime Minister Theresa May has urged the Iranian president to resolve the case of a British-Iranian aid worker who faces trial in Iran.
May's office said on August 9 she had "raised concerns" about Nazanin Zaghari-Ratcliffe and other dual nationals during a telephone call with President Hassan Rohani.
May "stressed the importance of resolving these cases as we worked to strengthen our diplomatic relationship," it added.
Zaghari-Ratcliffe, who has been detained since early April, is accused of trying to overthrow Iran's government.
Her husband has dismissed the allegation.
Several Iranian dual nationals from the United States, Britain, Canada, and France have been detained in the past months and are being kept behind bars on various charges.
Iran and Britain have been rebuilding their diplomatic relationship since reopening their respective embassies in 2015, after Tehran and world powers struck a deal on Iran's nuclear program.