Theresa May is to travel to a historic European city to unveil further details of her vision for Britain's future outside the EU.
The Prime Minister's high-profile Brexit speech in the Italian city of Florence on September 22 is likely to be seen as a bid to break the deadlock in withdrawal negotiations, which resume in Brussels three days later.
It comes amid warnings progress in talks on the UK's divorce deal has been too slow for discussions to move on to the question of a future trading relationship as Britain desires.
EU chief negotiator Michel Barnier has said no "decisive progress" was made on issues like citizens' rights and Britain's financial settlement in the last round of talks in August.
The state of talks was "quite far" from being advanced enough for the leaders of the 27 remaining EU nations to authorise the opening of negotiations on the future relationship in October as planned, he warned.
Former European Council president Herman van Rompuy said the chances of moving to the second phase of negotiations next month were "in the neighbourhood of zero".
Downing Street declined to discuss the content of Mrs May's speech, beyond saying she will give an "update on Brexit negotiations so far" and will "underline the Government's wish for a deep and special partnership with the European Union once the UK leaves the EU".
Speculation is rife she will seek to use the opportunity to make a breakthrough on some of the areas which are blocking progress in talks, such as the EU's demand for payments of £50 billion or more to cover remaining UK liabilities.
The fourth round of formal talks had initially been pencilled in for the week of September 18 but Mrs May's official spokesman denied the delay was caused by the timing of the PM's speech.
"Both sides settled on the date for that round after discussions between senior officials in recognition that more time would give negotiators flexibility to make further progress," he said.
Explaining her choice of venue, the spokesman said: "The PM 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."
Mrs May travelled to Italy within days of taking office in July 2016 for talks with then prime minister Matteo Renzi on her plans for Brexit.
She was hosted by Renzi's successor Paolo Gentiloni for this year's G7 summit in Sicily and then spent part of her summer holiday walking in the mountains of northern Italy.
Downing Street declined to say whether Mrs May would hold talks with Mr Gentiloni during her visit or whether the Italian PM would attend her speech.