European leaders should not allow Brexit talks to progress due to a "very disturbing" deadlock on the UK's exit bill, the EU's chief negotiator has declared.
Michel Barnier revealed he would again advise the EU27 not to progress to talks on a future trade relationship when leaders gather in Brussels on 19 October.
At a joint news conference with Brexit Secretary David Davis, following the conclusion of the fifth round of Brexit negotiations, Mr Barnier claimed the latest talks had not made "any great steps forward".
In response, Mr Davis pointed to "significant progress" since negotiations first began in June as he attempted to pressure the EU to loosen its strict negotiating guidelines.
Mr Barnier said he would not be able to report "sufficient progress" on the key withdrawal issues - the financial settlement, citizens' rights and Northern Ireland - for him to tell EU leaders to sanction the second phase of negotiations.
His comments saw the pound sterling sink against both the dollar and euro.
The European Commission official said the Brexit bill remained a key sticking point in talks, with "technical discussions" but no formal negotiations on the subject this week.
"We are at a state of deadlock on this question, which is very disturbing," he said, before declaring the EU would not make "concessions" on any of the three divorce issues.
Mr Davis admitted there was still "much work" to be done, but said there had been movement on divorce issues, including a "rigorous examination" of the financial settlement by UK officials.
The Brexit Secretary also highlighted how some withdrawal issues were "dependent on discussions on our future relationship".
He said: "I make no secret of the fact that to provide certainty we must talk about the future."
UK sources close to the negotiations told Sky News the UK will not budge one bit over the financial settlement until the EU offers some slack over the sequencing of talks.
Mr Davis expressed his hope the EU27 will hand Mr Barnier "the means to progress" during Brexit negotiations, while the European Commission official himself vowed to "explore ways to get out of deadlock", adding: "Decisive progress is within our grasp."
Despite insisting he will "scrupulously" follow the framework for negotiations handed to him by the 27 EU member states, Mr Barnier offered some hope Brexit talks could progress before the end of the year.
He said: "With political will decisive progress is within our grasp within the next two months."
After next week's Brussels summit, EU leaders meet again on 14 December, before which Mr Barnier might finally recommend they authorise the next stage of negotiations.
Speaking later at a press conference in London alongside his Polish counterpart, Foreign Secretary Boris Johnson added to Mr Davis' efforts to force the EU into budging from its strict negotiating stance.
"We think we've made some very helpful suggestions to get the great ship moving down the slipway and onto the open seas," he said.
"That's what we all want to see, we see no reason why that should not take place and we're looking for some urgency from our friends and partners and time to put a bit of a tiger in the tank and get this thing done."
Following the news conference in Brussels, Labour's shadow Brexit secretary Sir Keir Starmer urged Mr Davis to request an additional emergency round of talks before next week's European Council summit.
Later, during a visit to a community centre in Shipley, West Yorkshire, Jeremy Corbyn said his views had not changed on Britain's EU membership.
Asked whether he would still vote Remain at a second EU referendum, after the Prime Minister dodged the same question earlier this week, the Labour leader insisted "there isn't going to be another referendum".
"I voted Remain because I thought the best option was to remain," Mr Corbyn added.
"I haven't changed my mind on that but we accept the result of the referendum."