The United States said Thursday that Iran has given no hint that it wants to return to stalled talks over reviving the Iranian nuclear deal.
"For now, certainly there's no indication, positive indication that Iran is prepared to come back... and to try to close down the remaining issues," a senior US official said.
"We don't have direct interaction with the Iranians so it's hard for us to assess levels of optimism and pessimism," said the official in a briefing to journalists.
He said "nothing has happened" to make the United States optimistic.
"We've not heard anything through indirectly about a date, or about Iran's intentions to continue the work that was begun in Vienna and try to close those gaps.
"The window opportunity is open and won't be open forever," he added.
The Joint Comprehensive Plan of Action is the agreement the United States, China, Russia, Germany, France and Britain reached with Iran on Tehran's nuclear program in 2015.