A tweet from Iran President Hassan Rouhani's official account was deleted Monday just moments after he indicated a deal on the Islamic republic's nuclear programme had been reached.
"#IranDeal is the victory of diplomacy & mutual respect over the outdated paradigm of exclusion & coercion. And this is a good beginning," the message said.
Having sought to end the nuclear crisis -- and with it the international sanctions that have paralysed Iran's economy -- Rouhani's fate is often seen as inextricably linked to the negotiations.
With officials in Vienna saying the chances of an accord being agreed on Monday were slim, the tweet swiftly disappeared from Rouhani's Twitter feed.
The president's sole English-language Twitter account -- a parallel one in Persian was also deleted -- is thought to be run by his media department.
He later sent a new tweet which was more muted.
"If #IranDeal, victory of diplomacy and mutual respect over outdated paradigm of exclusion and coercion. And this will be good beginning," it said.
Rouhani had been expected to address the nation on state television late Monday amid reports that a deal with world powers was close, but those plans appear to have been postponed.
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The official IRNA news agency said Rouhani would speak when the nuclear talks have concluded, but it did not give a time.
There had been optimism a deal would be clinched over the weekend, but positive statements have been followed by talk of unresolved issues between the two sides.
Finalising a framework accord struck in April has proved difficult, with talks stumbling on the exact timing of sanctions relief and Iran's desire to have a UN conventional arms embargo lifted.
Deadlines of June 30 and July 7 were missed, but Iran and the six powers -- Britain, China, France, Russia and the United States plus Germany -- have continued to talk in the Austrian capital.
Rouhani late Sunday raised expectations that an agreement to end the 13-year dispute about Iran's nuclear programme was at hand.
"We have come a long way. We need to reach a peak and we're very close," Rouhani said, quoted by the ISNA news agency on what was the 16th day of the Vienna talks.
"We are so close that if you look down from below you feel as if we have got there, but when you do get there you know there are still some steps to take."
Iran denies Western suspicions that it is developing a nuclear bomb.