"On Friday, September 22nd, the prime minister will give a speech in Florence to update on Brexit negotiations so far," her spokesman said. "She will underline the government's wish for a deep and special partnership with the European Union once the UK leaves the EU."
Asked about the choice of venue, he said: "The prime minister wanted to give a speech on the UK's future relationship with Europe in its historical heart.
"The UK has had deep cultural and economic ties spanning centuries with Florence, a city known for its historical trading power.
"As the UK leaves the EU, we will retain those close ties. As the prime minister has said many times, we are leaving the EU not Europe."
May gave formal notification to Brussels of Britain's intention to leave the 28-nation bloc in March, starting the two-year countdown to Brexit.
But negotiations with the EU are proceeding slowly, as both sides grapple over the extent of Britain's financial obligations, the rights of European citizens and the issue of the Irish border.
The British government announced Tuesday that the fourth round of talks, which were due to start next week, had been postponed until September 25.
The decision was taken by "both sides" to allow more time for consultation, with the aim of giving negotiations "the flexibility to make progress", a spokesman said.
European Parliament Brexit chief Guy Verhofstadt said last week that the talks could be delayed because of an "important intervention" from May.
Her spokesman said: "The prime minister has said that she would provide updates on how the negotiations were going and be engaged in an ongoing conversation with Europe, and that's what she's doing."