Three months ago there were a number of unresolved issues, the official said, asking not to be identified. But now "there are only a few items left which need to be tackled by the ministers. That is why the ministers are here," he said, speaking as top diplomats began crunch talks to try and secure a deal.
The nuclear talks have dragged on for almost two years, and according to a report from Reuters the manager of a local brothel in Vienna said that “business is booming” - suggesting it's not all work for the hordes of diplomats, officials, security agents and reporters who have descended on the Austrian capital.
He declined to say who were his most frequent customers, but said that as far as he was concerned, the longer the negotiations between Iran and the six world powers (the United States, Russia, China, Britain, France and Germany) drag on, the better.
Brothels are legal in Austria. Last month one Austrian establishment announced it was offering customers free sex in a summer-long protest over what it views as punitive taxes.
Vienna's luxury Palais Coburg hotel has hosted most rounds of the talks since February 2014, and rumours have circulated about a network of underground tunnels connecting it to brothels and other establishments - but this could well be a myth.
With temperatures in Vienna soaring up to 37C, keeping cool has become a priority for many television crews and photographers - with shorts and t-shirts replacing shirts and ties in some cases.
The Austrian Foreign Ministry has also been supplying free ice cream to the media tent - which thankfully does have air conditioning.
This round of talks in Vienna has already busted through a June 30th deadline, and is now in its tenth straight day.
But all sides have insisted they are not planning a further extension beyond Tuesday's new deadline.
The Iranian delegation had not even discussed "a possible extension because extension to be honest is not in anybody's interest," an official told AFP.