Prior to this week's negotiation, rumors were circulating that Britain proposed to pay 20 billion euros (23.6 billion US dollars) for the "divorce."

In her speech in Florence, May reassured her European partners that the EU27 would not need to pay more or receive less over the remainder of the current EU budget plan as a result of Brexit.

Commenting on May's Brexit speech in Florence, Barnier said her speech had created a "new dynamic in talks."

Barnier, however, warned: "We will need several weeks, even several months, to be able to see sufficient progress on the principles of this orderly departure."

He also said an expert group held detailed talks on some technical aspects of the financial settlement and those talks were useful.

"This week, the UK negotiating team made clear that applying the first principle (May's principle) would be limited to 2019-2020. The UK explained also that it is not in a position yet to identify its commitments taken during membership," said Barnier, asserting that for the EU the only way to reach sufficient progress is that all commitments undertaken between the EU28 are honored.

Davis said Britain has explained this reassurance in detail to the Commission and that Britain would honor its commitments made during the period of its membership.

But, "we are not yet at the stage of specifying exactly what these commitments are. That will need to come later," said Davis.