European Commission president Jean-Claude Juncker has warned it would take “miracles” for trade talks between the UK and EU to begin before the end of October.
The EU has insisted that it will not discuss its future relationship with Britain until an agreement is reached on the divorce settlement.
Brussels wants to strike a deal on the rights of EU citizens living in the UK, how much money the UK will pay as it exits the bloc and how the Northern Ireland border will function.
Speaking at a European summit in Estonia on Friday, Juncker warned: “By the end of October we will not have sufficient progress.
“I am saying that that there will be no sufficient progress from now until October unless miracles would happen.”
His comments echo those of the EU’s chief Brexit negotiator Michel Barnier, who yesterday said it could be “months” until trade talks begin.
Brexit secretary David Davis has insisted that “considerable progress” was made during this week’s round of talks.
Theresa May, who is in Estonia for the meeting, said Brexit did not mean the UK was abandoning its European allies.
“While we are leaving the European Union, as I have said many times, we are not leaving Europe so the United Kingdom is unconditionally committed to maintaining Europe’s security,” the prime minister said.
“When a nation like Russia violates the rules-based international order that we have worked so hard to create, we must come together with our allies to defend that international system and the liberal values, human rights and the rule of law by which we stand,” she said.
She added: “I am clear that Britain will always stand with our allies in defence of these values.”