Prime Minister Theresa May said Monday there is a positive "new dynamic" in Brexit talks, with Britain and the European Union nearing agreement on the rights of 4 million citizens whose lives will be affected by the split.
May urged European Union officials to show "leadership and flexibility" in negotiations on Britain's exit, saying "the ball is in their court."
The EU, however, lobbed the ball straight back. European Commission spokesman Margaritis Schinas said the responsibility for progress is "entirely in the U.K. court."
More than a year has passed since Britain voted to leave the EU, and six months since Britain triggered the two-year countdown to its EU exit. A fifth round of divorce negotiations opened Monday in Brussels, with both sides frustrated by the lack of progress.
May told British lawmakers that "there is a new dynamic in the negotiations" since her major Brexit speech in Florence, Italy, last month.
In the Florence speech, May said Britain would be willing to abide by EU rules and pay into its coffers during a transition period of about two years after Brexit in 2019.
She also signalled Britain would pay what it owes to settle financial commitments it has made to the bloc, but without naming a figure.
EU leaders have called her suggestions positive but asked for more details. Few were forthcoming in May's statement on Monday, though she did say that Britain might accept the jurisdiction of the European Court of Justice during the transition period — an idea that infuriates many pro-Brexit members of her Conservative Party.
The U.K is increasingly anxious to move talks on to discussing future trade relations, but so far the EU says there hasn't been "sufficient progress" on the major divorce terms — the size of the Brexit bill, the status of the border between Ireland and Northern Ireland and the rights of 3 million EU citizens living in Britain and 1 million Britons in other member states.
May said progress was being made on all three, and "there is considerable agreement" between the U.K. and the bloc on citizens' rights.
"So I hope our negotiating teams can now reach full agreement quickly," she said.
Schinas, the EU spokesman, said "there has been so far no solution found on step one, which is the divorce proceedings."
"So the ball is entirely in the U.K. court for the rest to happen," he said.
Danish Foreign Minister Kristian Jensen, however, called for compromise, saying "this will never be a 100 per cent win for one side or the other side."
Jensen said the sides "are now on the same page" and "it is rather important we get on to a more close and more speedy process of concluding some of the issues."
May told lawmakers she believed the negotiators would "prove the doomsayers wrong," but also said Britain was planning for the possibility of leaving the EU without a deal.
Critics have accused the government of failing to prepare for a "no deal" Brexit, which would mean an end to tariff-free trade with the EU.
On Monday the government published papers on trade and customs which May said would pave the way for Britain to "achieve the greatest possible tariff and barrier-free trade" after Brexit, even if there is no trade deal with Brussels.
May addressed Parliament on its first day back since her disastrous speech to the Conservative conference last week, which saw her bedeviled by a prankster, a sore throat and a malfunctioning set.
The debacle intensified debate about whether May can unite her fractious government — divided between Brexit enthusiasts and more reluctant leavers — and how long she can survive as prime minister.
Labour Party leader Jeremy Corbyn accused the government of making a mess of the Brexit negotiations.
"Fifteen months on from the referendum, we're still no clearer what the future of this country will look like," he said.