President Barack Obama made diplomatic overtures to Iran before its June 12 election, but Clinton told the BBC: "We haven't had any response."
She added: "We've certainly reached out and made it clear that's what we'd be willing to do, even now, despite our absolute condemnation of what they've done in the election and since, but I don't think they have any capacity to make that kind of decision right now."
Her comments were published on the BBC's website.
The re-election of President Mahmoud Ahmadinejad, in a poll the opposition denounced as rigged, triggered days of mass street protests in which at least 20 people were killed.
The contested vote and the authorities' harsh response to the unrest have divided Iran's ruling elite.
Washington and Tehran have had hostile relations since the 1979 Iranian revolution. Iran rejects U.S. suspicions it seeks to develop nuclear weapons under cover of a civilian atomic energy program
(Editing by Jon Boyle)
