"Keep in mind that there are differences between public and private statements," he said, adding that "there have been conversations" between Iran and Britain, France and Germany "and we expect the Iranians to provide a proper answer within the span of weeks and not months."
Later, pushed on whether he had meant to signal that Iran’s private responses were more positive than its public statements, Snow replied: "I make absolutely no attempt to characterize — good, bad, or indifferent."
"So I’m not trying to tell you that there have been positive signs through those," the spokesman said.
A White House official, who requested anonymity, said that US allies were in touch with decision-makers in Tehran but declined to characterize the tone of those talks, and said the emphasis was on awaiting a formal Iranian response.
Although Khamenei said Iran was ready to ease international concerns over its disputed atomic drive, he said that "negotiations with the United States are of no use for us. We have no need for such negotiations."
"We will not negotiate with anyone over the undeniable right of nuclear technology and using it," he added, again signalling Iran was unwilling to bow to international demands to suspend uranium enrichment.
On June 6, Solana presented Iran with an offer — which would pave the way for the first substantive contacts between Iran and the United States in decades — of multilateral talks and a variety of incentives.
The offer is conditional on Iran first agreeing to suspend enrichment work, the focus of suspicions that the Islamic regime wishes to acquire nuclear weapons.
The United States has insisted that Iran has "weeks, not months" to reply.
But Iran appears to still reject the key condition and continues to call for negotiations without any "preconditions".