"It's a good day for the people of Iran... and also a good day for the region. The sanctions will be lifted today," he said after arriving in Austria's capital, according to the ISNA news agency.
His comments came after diplomatic sources said the UN nuclear watchdog would likely say Iran had complied with last July's landmark agreement with world powers on Tehran's atomic programme. Zarif, who led Iran in nuclear talks with the United States, Britain, China, France, Russia and Germany, said the deal had removed from the Middle East "the shadow of a baseless confrontation".
"It proved that we can solve important problems through diplomacy, not threats and pressure, and thus today is definitely an important day," he added.
The International Atomic Energy Agency report will allow US Secretary of State John Kerry, Zarif and EU foreign policy chief Federica Mogherini, to announce in Vienna that the deal can enter into force, the diplomatic sources said.
Under the July 14 deal, Iran agreed to scale down dramatically key areas of its nuclear activities in exchange for relief from crippling sanctions, notably on Tehran's oil exports. These steps, combined with tighter IAEA inspections, extend to at least one year -- from just a few months previously -- how long Iran would need to make enough fissile material for one nuclear bomb. Iran has always denied seeking an atomic weapon, saying its activities are only for peaceful purposes such as power generation and medical research.