Iran claimed on Sunday that a deal had been reached on exchanging British and American prisoners - including Nazanin Zaghari-Ratcliffe - for Iranian prisoners and funds, but the United States promptly dismissed the reports as false.
According to Iranian state TV, an unnamed Iranian official claimed that a deal had been finalised where Ms Zaghari-Ratcliffe would be released as soon as the UK repays a 1970s-era arms debt.
The official also claimed that Tehran and Washington have agreed on a deal to swap prisoners and to release Iranian funds held in the United States.
"The release of Nazanin Zaghari-Ratcliffe in exchange for the UK's payment of its 400 million pound-debt to Iran has also been finalized," the official said.
However, the UK played down those report and said discussions were ongoing, while the United States said reports of a US-Iran prisoner swap were "not true".
A spokesman for the UK Foreign Office said: "We continue to explore options to resolve this 40-year-old case and will not comment further as legal discussions are ongoing."
A US state department spokesman said: "Reports that a prisoner swap deal has been reached with Iran are not true. As we have said, we always raise the cases of Americans detained or missing in Iran. We will not stop until we are able to reunite them with their families."
Jake Sullivan, the US national security adviser, said the US had "not yet reached agreement" with Iran, adding that "there's still fair distance to travel to close the remaining gaps."
Tulip Siddiq, the Labour MP who is in close contact with Ms Zaghari-Ratcliffe's family, also said there had been no confirmation so far.
"I am aware there are news reports circulating about the debt being paid to #FreeNazanin. I have spoken to her family and they have heard nothing confirming any of these rumours," she wrote on Twitter.
Mz Zaghari-Ratcliffe has already completed a five-year prison sentence in Iran on dubious spying charges.
She was also sentenced to an additional year in prison last week on charges of plotting to overthrow the Islamic Republic, which she also strongly denies.
This is a breaking story. More to follow.