The senior official, speaking on condition of anonymity, said the EU's negotiator on the file, Enrique Mora, attended Raisi's swearing-in in Tehran last Thursday and spoke with the Iranian official designated to take charge of the nuclear talks, Hossein Amir-Abdollahian.
Amir-Abdollahian "is supposed to be the new foreign minister" in Raisi's cabinet, but that has not yet been announced, the EU official said.
He added that it was unclear whether the nuclear talks would remain under the responsibility of the Iranian foreign ministry or be taken over by another body, such as Iran's National Security Council.
Raisi is a hardliner expected to consolidate the ultraconservatives' power during his four-year term.
He succeeds the relatively moderate Hassan Rouhani whose landmark achievement during his own two-term presidency was the 2015 nuclear agreement between Iran and six world powers: the five permanent members of the UN Security Council plus Germany.
Former US president Donald Trump pulled out of the deal in 2018 and re-imposed sanctions that have choked Iran's oil-dependent economy. Iran responded by walking back measures it had agreed to abide by.
Talks have been happening since April in Vienna to find a way to bring both sides back into full compliance.
The last round took place on June 20 with no date set for when they would continue. The EU chairs the meetings.
The United States has said it is "an urgent priority" to get Iran back to the table.
But tensions have risen, notably with an attack by drones last week on an Israeli-linked tanker off Oman that killed a Briton and a Romanian on board.
The G7 -- the United States, Britain, Canada, France, Germany, Italy and Japan -- blamed the attack on Iran. Tehran denies the accusation.
Iran's decisions to increase uranium enrichment and restrict UN inspectors' access to some nuclear facilities have unsettled the West.
"The EU would like Iran to freeze the nuclear activities," the EU official said, but admitted Russia and China did not back its language on that position.
He added that Mora's meeting with Amir-Abdollahian was "very useful", even though many issues remain unclear.
The Iranians said they want to get back to Vienna "as soon as possible, not just for talks but to achieve an agreement -- they want a success," the EU official said.
He added that the Iranians had not mentioned any changes to their position in the talks, and Mora had informed the United States of the substance of his talks with Amir-Abdollahian.
"If there is no agreement, the situation for Iran will be much worse," the EU official predicted. "We will work on the assumption we will get an agreement."
