Washington is denying a report by Iranian state-run television that "prisoner swap" deals were struck to free detained US dual citizens in Iran.
Prisoner swaps between the US and Iran are not uncommon and both countries in recent years have routinely sought the release of detainees.
But any movement between the two countries is particularly sensitive as the Biden administration seeks to restart nuclear talks. A 2015 nuclear deal between the nations included prisoner exchanges.
The issue burst into public view with a report on Sunday in Iran of a deal to release US and British prisoners in exchange for Tehran receiving billions of dollars.
US officials immediately rejected the report, although one source said talks are active, with messages being passed through intermediaries.
It was not immediately clear if the report was a move by the hardliners running the Iranian broadcaster to disrupt negotiations with the West amid talks in Vienna on the tattered nuclear deal.
Even after an initial American rejection , a newsreader on Iranian state TV repeated the announcement.
“Some sources say four Iranian prisoners are to be released and $7 billion is to be received by Iran in exchange for releasing four American spies,” she said.
She described the purported deal as a product of congressional pressure on US President Joe Biden and "his urgent need to show progress made in the Iran case".
But Iran’s ambassador to the UN, Majid Takht e Ravanchi, later rejected the report of the prisoner swap, saying that it’s “not confirmed”.
“Iran has always emphasised the comprehensive exchange of prisoners between the two countries,” he said, without elaborating.
State-run TV did not identify the Iranians that Tehran sought to be freed.
US State Department spokesman Ned Price immediately denied the Iranian state TV report.
“Reports that a prisoner swap deal has been reached are not true,” Mr Price said.
“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.”
Mr Biden's chief of staff Ron Klain told CBS that "unfortunately, that report is untrue. There is no agreement to release these four Americans".
“We’re working very hard to get them released,” Mr Klain said. “We raise this with Iran and our interlocutors all the time, but so far there’s no agreement.”
Tehran holds four known Americans in prison: Baquer and Siamak Namazi, environmentalist Morad Tahbaz and Iranian-American businessman Emad Shargi. Iran long has been accused of holding those with Western ties prisoners to be later used as bargaining chips in negotiations.
Despite the US denials, there are signs that a deal on prisoners may be in the works based on Iranian officials’ remarks in recent weeks.
Although no formal proposal for a swap has yet been presented to officials in Washington, let alone agreed to by the White House, the specificity of the reports from Iran suggested that working-level consideration of a deal is at least under way.
Iranian state TV also quoted sources as saying a deal had been reached for the UK to pay $552 million) for the release of British-Iranian woman Nazanin Zaghari-Ratcliffe.