UK Foreign Secretary Boris Johnson said he plans to express his "grave concerns" about dual British-Iranian nationals during his visit Saturday to Iran in an apparent reference to imprisoned mother Nazanin Zaghari-Ratcliffe.
Johnson is due to meet with his Iranian counterpart, Mohammad Javad Zarif, in Tehran in the first visit by a UK foreign secretary to the Middle Eastern country since 2015.
Nazanin Zaghari-Ratcliffe has been detained in Iran on espionage charges
Family insists British-Iranian citizen was on vacation when she was held in April 2016
Zaghari-Ratcliffe, who has been detained in Iran since April 2016 on espionage charges that she and her family vehemently deny, is expected to appear in court Sunday to face charges of "spreading propaganda."
Johnson's visit comes at a time of increased regional tensions.
He plans to discuss the crisis in Yemen and Britain's support for the 2015 nuclear deal struck between Iran and world powers "while making clear our concerns about some of Iran's activity in the region," according to his statement.
"We will also discuss our bilateral relationship and I will stress my grave concerns about our dual national consular cases and press for their release where there are humanitarian grounds to do so," he said.
Iranian Foreign Ministry spokesman Bahram Qassemi said Johnson would discuss bilateral ties, particularly high-level economic cooperation between Tehran and London, in meetings with high-ranking Iranian officials.
The British and Iranian sides will also exchange views on the expansion of business ties, regional issues and international developments, he said.
Zaghari-Ratcliffe has found herself at the center of an international dispute following an error by Johnson, who mistakenly told a British parliamentary committee last month that the British-Iranian citizen was in Iran teaching journalists when she was detained.
Johnson later backtracked and apologized for his remarks, saying she was in Iran on holiday.
Zaghari-Ratcliffe's family and employer have always insisted she was visiting family on vacation, which is also the official position of the British government.
The seriousness of Johnson's error became apparent days later when Zaghari-Ratcliffe was summoned to an unscheduled court hearing at which the foreign secretary's remarks were cited as proof she had engaged in "propaganda against the regime."
Her family fears the five-year sentence she was given on espionage charges could be lengthened.
Zaghari-Ratcliffe was detained at the airport in Tehran in April 2016 on her way back to the UK from visiting family with her daughter Gabriella, then 22 months old. The child has since been looked after by her maternal grandparents.
Zaghari-Ratcliffe's husband, Richard Ratcliffe, told Britain's Guardian newspaper he was "waiting on tenterhooks" ahead of Johnson's visit to Tehran.
"I'm really pleased he is there in time for Nazanin's trial and waiting to see what will happen, and trying not to have too clear expectations at all," he is quoted as saying.
Johnson's visit to Iran is only the third by a foreign secretary since 2003, the UK Foreign Office said. His three-day tour of the Middle East began Friday in Oman and will conclude with a stop Sunday in the United Arab Emirates.