U.K. Brexit Secretary David David listens to the EU's chief negotiator Michel Barnier | Thierry Charlier/AFP via Getty Images EU ‘increasingly doubtful’ Brexit talks will move to phase 2 in October The UK wants to discuss post-Brexit trade but the EU insists that negotiations make sufficient progress on the divorce first.

Top EU officials are "increasingly doubtful" that Brexit talks will move on to their second phase of discussing trade in October, according to three senior diplomats briefed ahead of next week's round of negotiations.

The skepticism from the EU side emerged at a key all-day meeting in Brussels Thursday. At the meeting, diplomats from the 27 remaining EU member countries were briefed on the bloc’s position by a senior member of chief negotiator Michel Barnier's team.

"It is clearly worrying that we have major differences on core issues such as direct effect [the application of EU law in the U.K.], the ECJ [the role of the European Court of Justice] and financial obligations [the so-called Brexit bill]," said a senior diplomat who attended the meeting.

Asked about the content of the briefing, they said: "With very little time to land all this, even if U.K. moves [on key EU demands] 'sufficient progress' in October appears to be increasingly doubtful."

“The British need to be shaken a bit and the only way to force reality in London is for the Commission and the Council to be strict" — Andrew Duff, former British MEP

October is key because that's when EU leaders will decide at a European Council summit whether "sufficient progress" has been made in the talks on three separation issues — the Brexit bill, the rights of EU citizens in Britain post-Brexit (and vice versa) and the Northern Irish border.

On Monday, Barnier underlined the importance of moving forward on the three issues next week. "Essential to make progress on citizens rights, settling accounts and Ireland," he tweeted.

Andrew Duff, a former British MEP who has been following the talks closely, agreed that it "looks unlikely" there will be a breakthrough by October. "There could be a surprise from the British Treasury — that they will explain their methodology to calculate the [Brexit] bill — but I don't see that happening."

“The British need to be shaken a bit and the only way to force reality in London is for the Commission and the Council to be strict and to apply the criteria that have been agreed," he said. "It is clear that so far the British have failed to be sufficiently precise and sufficiently constructive on the three separation issues."

At the meeting on Thursday, Stéphanie Riso, a senior member of the EU’s Brexit negotiating team, also discussed with EU diplomats the bloc’s reaction to U.K. position papers released last week on post-Brexit customs arrangements and the Northern Irish border.

The papers are seen as a gesture of positive engagement by the Brits but they are "only somewhat appreciated," said a second diplomat who attend the meeting. "They are not clear, they have not enough details and are often far from reality," the diplomat said, adding that Barnier's team expressed "no big hopes for the next round on the big first phase issues."

The EU regards the flurry of documents from the U.K. as a distraction tactic, designed to pressure its negotiators into talking about future trade.

Another EU diplomat described the papers as a "mix of good and bad." But they objected to what they see as the U.K.'s attempt to blur the strict sequencing of the talks. "[The] U.K. tries to import phase two stuff into papers for phase one, or at least blur the lines between them."

In the two weeks running up to the talks, the U.K. government has been bombarding its EU counterparts with a series of position papers on everything from future customs arrangements to the handling of confidential documents.

But the majority of the proposals refer to the U.K.’s future relationship with the bloc, rather than the separation issues that the EU wants to tackle first. It regards the flurry of documents from the U.K. as a distraction tactic, designed to pressure its negotiators into talking about future trade.