Britain and the EU took "decisive steps forward" in Brexit talks following a key speech by Prime Minister Theresa May but more work is needed to unlock the next phase, negotiators said Thursday.

Speaking after the fourth round of talks in Brussels, European Union negotiator Michel Barnier and his British counterpart David Davis said there was now more clarity on the details of May's speech in Florence last week.

But France's Barnier warned they were "weeks or months" away from making the progress on divorce issues needed to move on to discussions on a future trade deal after Britain leaves in March 2019.

"Thanks to the constructive and determined manner in which both sides have conducted these negotiations I believe we are making decisive steps forward," Davis told a news conference alongside Barnier at the European Commission's headquarters.

EU leaders are set to decide at a summit in October whether there has been "sufficient progress" on three divorce issues: Britain's exit bill, the fate of Northern Ireland, and the rights of three million EU citizens living in Britain after its departure from the bloc.

- 'New dynamic' -

May's Florence speech offered key concessions as well as proposing a transition period of around two years after Brexit Day to allow businesses to adjust to the new situation.

But Barnier took a more cautious tone than Davis, saying that while May's speech had given a "new dynamic" to the talks and created clarity, there was still more work to be done.

"We are not there yet," Barnier warned.

"It will take several weeks or months until we can say there is sufficient progress on the principles of an orderly withdrawal."

The next round of talks starts on October 9 and key differences remain, with Davis highlighting the fact that EU citizens would have their rights protected by British courts, but Barnier insisting the the European Court of Justice must be paramount.

Barnier also insisted there could be "no possible link" between Britain's divorce bill and a future trade deal, saying that the financial settlement --  estimated by the EU at between 60 and 100 billion euros -- must be agreed first.

Davis said earlier this week that the two went hand in hand, with Britain apparently keen to keep money -- its strongest negotiating tool -- in play until the very end of the negotiations.

The EU is committed to spending a record 238.8 billion euros on future projects and needs to find a way to fill the financial hole left when Britain -- which currently contributes around 12 percent of the budget -- quits.

Barnier also insisted that any transition deal should be discussed in the second phase of talks.

- MEPs urge delay -

Separately, the European Parliament said in a draft resolution to be voted on next week that EU leaders should postpone their decision on progress until after their October summit.

The resolution said the European Parliament "is of the opinion that in the fourth round of negotiations sufficient progress has not yet been made on citizens' rights, Ireland and the Northern Ireland, and the settlement of the United Kingdom's financial obligations."

The parliament "calls on the European Council, unless there is major breakthrough in line with this resolution in all three areas during the fifth negotiation round, to decide at its October meeting to postpone its assessment on whether sufficient progress has been made".

MEPs will have the final say on any deal for Britain's departure from the EU in 2019.

European Council President Donald Tusk, who represents the EU member states, said after meeting May in London on Tuesday that there was "no sufficient progress" so far.

The British premier is set to meet her EU counterparts at a summit in Tallinn, Estonia, later Thursday, which will focus on French President Emmanuel Macron's vision for the future of the bloc.

Britain voted to leave the EU in a shock referendum result in June 2016.