The EU's top official has warned it will take "miracles" for Brexit talks to move on to their next phase by the end of October.
European Commission President Jean-Claude Juncker offered a gloomy verdict on the chances of Brexit negotiations progressing from divorce issues to future trading arrangements within the next month.
The EU has demanded "sufficient progress" be reached on three key withdrawal topics - the financial settlement, EU citizens' rights and Northern Ireland's border - before the UK is allowed to discuss the British Prime Minister's wish for a "comprehensive and ambitious" UK-EU trade deal.
Theresa May had hoped her major Brexit intervention in Florence last week would help push negotiations forward - perhaps in time for EU leaders to authorise the start of trade talks at a European Council summit on 19 October.
However, speaking at an EU digital summit in Estonia today, Mr Juncker said: "By the end of October we will not have sufficient progress.
"At the end of this week I am saying that that there will be no sufficient progress from now until October unless miracles would happen," he said.
Mr Juncker appeared much less optimistic over the advancement of Brexit talks than EU chief negotiator Michel Barnier, who completed the latest round of discussions on Thursday.
Despite warning it could take "several months" for the key divorce issues to be decided, Mr Barnier hailed a "new dynamic" to negotiations following Mrs May's speech.
At the start of Friday's summit in Estonian capital Tallinn, Mrs May said she was "pleased the negotiations have been making progress".
She also held a bilateral meeting with freshly re-elected German Chancellor Angela Merkel on the sidelines of the EU gathering, their first since the PM's speech.
Downing Street revealed Mrs May noted the "constructive" response to her intervention, which had been "intended to create momentum."
The German Chancellor was said to have "welcomed" the speech and described "good progress" in negotiations this week.
"The Prime Minister and the Chancellor both agreed on the importance of settling the issue of citizens' rights at the earliest opportunity," a spokesperson said.
"The Prime Minister pointed to the commitment made in her Florence speech to incorporate the agreement reached on citizens' rights fully into UK law and make sure the UK courts can refer directly to it."
The two leaders also discussed Mrs May's plan for a two-year implementation period for a Brexit deal.
Despite offering the concession during her address in Italy, a major stumbling point in negotiations remains over whether the European Court of Justice (ECJ) should play a role in guaranteeing the rights of EU citizens in the UK after Brexit.
Mrs May has previously vowed to end the influence of ECJ judges over Britain.
Earlier today, she used an address to some of the 800 British troops deployed to the NATO mission in Estonia to reassure EU leaders the UK will remain "unconditionally committed" to Europe's security after Brexit.