0249 GMT September 19, 2019
"As we look forward to the next stage, the ball is in their court. But I am optimistic we will receive a positive response," May told the British parliament on Monday. "I believe we can prove the doomsayers wrong."
The comments came after the prime minister gave assurances, in a speech in Italy last month, on payments to the bloc and EU citizens' rights.
This fifth round of Brexit negotiations is the last before European leaders meet next week to decide whether there is "sufficient progress" to move on to the trade talks as demanded by the UK.
“We should concentrate our negotiating time and capital on what really matters: the future long-term relationship we will have with the EU after this temporary period ends,” May said.
"Achieving that partnership will require leadership and flexibility, not just from us but from our friends, the 27 nations of the EU," she added. "And as we look forward to the next stage, the ball is in their court. But I am optimistic we will receive a positive response."
However, opposition Labour Leader Jeremy Corbyn said "no real progress has been made" with the EU in the 15 months since the Brexit referendum.
"The question has to be asked - what on earth has the government been doing all this time?" Corbyn added.
The European Commission hit back at May’s stance on Brexit, warning Britain still has more work to do before the two sides can reach a deal.
'Not exactly a ball game'
“This is not exactly a ball game,” Margaritis Schinas, the commission’s chief spokesman, told reporters in Brussels.
“There has been, so far, no solution found on step one, which is the divorce proceedings, so the ball is entirely in the UK’s court for the rest to happen,” he maintained.
British officials said Monday that Brexit Secretary David Davis would not be travelling to Brussels for the divorce talks, underscoring low expectations for the talks.
Schinas said the pace of the negotiations would depend on the presence of British negotiators. “The European Commission Article 50 team is available 24/7, the timing of talks depends on the availability of our UK partners. We are always here and we are ready,” he said.
Chief EU negotiator Michel Barnier was also not attending the start of the talks.
Brussels is alarmed by the leadership crisis that has embroiled the British premier, facing a plot to oust her following a mishap-strewn speech at her Conservative Party's annual conference.
The questions over May's leadership have dashed hopes that her Florence speech could give a "new dynamic" to the negotiations going forward.
Britain began the two-year process of leaving the bloc six months ago, but the talks have stalled on all three of the key Brexit issues – an exit bill, the rights of EU citizens and the fate of the border between Northern Ireland and Ireland.