British Foreign Secretary Dominic Raab said it would be beyond the pale for Iranian-British aid worker Nazanin Zaghari-Ratcliffe to be returned to detention in Iran at this time.
He added that Britain was still engaged in a process of paying back a debt it owns to Iran but that this was "not linked but in parallel" to the legal case.
"There's been a process that has been ongoing," he told Sky News about the debt dating back to 1979. "It's not linked but it's in parallel, where we've been saying look we recognize this debt and we'll look at how we can resolve it as best we can.
"Frankly that is separate from the clear and immediate obligation on the right to not to detain British nationals.
"It will be beyond the pale, for her to be returned to detention at this time."
Zaghari-Ratcliffe has spent more than four years in jail or under house arrest since being arrested in the Iranian capital in April 2016 while visiting relatives with her young daughter.
Zaghari-Ratcliffe, who worked for the Thomson Reuters Foundation -- the media organization’s philanthropic arm -- denied charges of sedition but was convicted and jailed for five years.