"If Brazil is willing to accept... this woman, we would hope that Iran would consider that as a humanitarian gesture," State Department spokesman Philip Crowley said.
"And the fact that Brazil has stepped up and indicated a willingness to resolve it, we hope Iran will listen."
The comments came after Brazilian President Luiz Inacio Lula da Silva on Saturday offered asylum to Sakineh Mohammadi-Ashtiani, a 43-year-old Iranian mother of two.
She was sentenced to death by stoning after being convicted in 2006 of having an extramarital affair during the trial of her husband's alleged murderer.
Lula appealed to Iranian authorities and Iran's President Mahmoud Ahmadinejad, a close ally of Brazil.
Mohammadi-Ashtiani's sentence sparked an outcry in Western countries, and was temporarily suspended earlier this month by Iranian judiciary chief Sadeq Larijani.