The European Union's chief Brexit negotiator says that talks on Britain's departure are weeks or months away from making sufficient progress, despite hailing a positive "new dynamic" in the negotiations.

Michel Barnier told reporters Thursday after a fourth round of talks that "we will need several weeks, even several months, to be able to see 'sufficient progress' on the principles of this orderly departure."

Britain is scheduled to leave the EU on March 29, 2019, but the talks must be wrapped by October 2018 to allow time for parliaments to ratify it. More than a year since Britons voted for Brexit, and six months on from its Brexit announcement, the talks are still in a preliminary phase. EU countries are concerned that time will run out, leaving a messy divorce that would be damaging to Britain and its European partners.

EU leaders insist the talks must make "sufficient progress" on Britain's financial settlement, the rights of citizens hit by Brexit and the status of the Ireland-Northern Ireland border before they can be broadened.

Britain says that future relations and trade are intertwined with the divorce settlement and that all elements should be discussed together.

EU leaders, minus British Prime Minister Theresa May, must rule whether "sufficient progress" has been made.

Britain's Brexit negotiator David Davis said that the talks were making good progress.

"We are making decisive steps forward," Davis said.

He said that, in particular, a lot of progress has been made on ensuring the rights of citizens who will be hit by Britain's departure.

"This round was a vital one. We made important progress," Davis said.

But he said the sides failed to agree on what role the European Court of Justice should play in the future.