The husband of Nazanin Zaghari-Ratcliffe said he was not optimistic about talks between UK Government officials and Iran’s deputy foreign minister.
The meeting on Thursday comes as Richard Ratcliffe endures his 19th day on hunger strike outside the Foreign, Commonwealth and Development Office (FCDO) in London.
Mr Ratcliffe began his demonstration last month after his wife lost her latest appeal in Iran, saying his family is “caught in a dispute between two states”.
Iranian deputy foreign minister, Ali Bagheri Kani, is meeting officials from the FCDO, and Mr Ratcliffe will meet Foreign Office minister James Cleverly afterwards.
Asked if he was feeling optimistic, Mr Ratcliffe told the PA news agency: “No, probably guarded. It’s a good sign the meeting’s happening and I don’t mean to disparage that.
“But I’ve had a lot of Foreign Office meetings where we’ve gone in with high expectations and come out deflated.
“I’m hoping the needle has moved in the last couple of weeks and there’s a realisation that the status quo isn’t enough.”
Mr Ratcliffe said the meeting “wasn’t on the cards until we started the protest, so there have been some effects”.
Ms Zaghari-Ratcliffe, a British-Iranian dual national, has been in custody in Iran since 2016 after being accused of plotting to overthrow the government.
She was taking the couple’s daughter, Gabriella, to see her family when she was arrested and sentenced to five years in jail, spending four years in Evin Prison and one under house arrest.
According to her family, she was told by Iranian authorities that she was being detained because of the UK’s failure to pay an outstanding £400 million debt to Iran.
Mr Ratcliffe has said the Government needs to do more to free his wife.
“I wouldn’t be camping here if the Government was doing enough,” he told PA.
He said the Government had known for years that Iran linked his wife’s imprisonment to debt owed to the country by the UK.
“The obvious thing that needs to be done is to settle that dispute and not allow innocent people to have their life wasted,” he said.
Mr Ratcliffe said he told Foreign Secretary Liz Truss at a meeting several weeks ago that the Government’s approach was failing.
He said: “We’ll have to meet her again. The first meeting did not go particularly well; the Foreign Office ended it early because the minister was travelling, so we’ll see at the next meeting if she’s more in command of and more persuasive in her answers.”
Mr Ratcliffe said he was not planning to immediately end his hunger strike.
“It’s definitely feeling harder and it’s definitely feeling like we’re in the last few days, but certainly able to go today and see what happens in the meeting of the ministers.
“We’re not going to be able to do it for much longer because my body is saying so.
“I think we are most likely to still be camping after the meeting, but I suppose that’s a decision to make then.”
He said a doctor had just checked him over and that he was in good condition.
Earlier, in an interview broadcast on BBC Radio 4’s Today Programme, Mr Ratcliffe said it was a breakthrough that the Iranians were coming to the capital.
“That’s a breakthrough, really. I think it’s been many years since an Iranian minister has come.
“This is the chief negotiator for Iran who is coming. Obviously our case is associated with all the wider manoeuvrings around the nuclear deal and everything else,” he said.
Mr Ratcliffe is on his second hunger strike in two years.
Previously, he camped in front of the Iranian Embassy for 15 days, a move he said had resulted in getting his daughter home.
During his latest demonstration he has been visited by supporters including Strictly Come Dancing co-host Claudia Winkleman, writer and presenter Victoria Coren Mitchell, and Labour leader Sir Keir Starmer.
Before Thursday’s meeting, a Foreign Office spokesman said: “We will urge Iran to take the opportunity to swiftly conclude the Joint Comprehensive Plan of Action (JCPoA) (nuclear) deal on the table.
“We will also be using this opportunity to again press firmly for the immediate release of our unfairly detained British nationals.”