U.K. Prime Minister Theresa May told Parliament Monday that while negotiations with the European Union have resulted in progress, the status of the Irish border has remained a critical stumbling block.

Over the weekend, rumors arose that a full withdrawal deal had been put in place after a sudden unscheduled meeting was announced between Britain’s Minister for Exiting the European Union, Dominic Raab, and the EU’s chief negotiator Michel Barnier.

However, it soon became clear that the sticking point of how to treat the border between Northern Ireland, which is part of the United Kingdom, and the Republic of Ireland, which is a member of the European Union, had again caused talks to stall.

Speaking in the House of Commons Monday afternoon, May insisted that the two sides were edging toward a deal: “I do not believe that the EU and the U.K. are far apart,” May said, to a mix of jeers and cheers.

May repeated to the U.K. Parliament that she would never accept a situation where there was a border in the Irish Sea, forcing Northern Ireland to be treated differently to the rest of the U.K.

A separate “backstop” arrangement has been discussed which would ensure no hard border between Northern Ireland and the Republic of Ireland, even if no formal Brexit deal can be reached.

It would mean Northern Ireland could stay in the customs union and select parts of the EU’s single market, therefore continuing a friction-free border with the Republic. The customs union is an agreement that allows partaking countries to set common external tariffs, allowing goods to travel freely between those countries. The single market is a deeper form of co-operation between member states that allows the free movement of goods, services, money and people in the bloc.

The U.K. government has said it wants a time limit placed on any such arrangement, while officials in Brussels say they are not prepared to agree to a time limit. May told lawmakers that any backstop shouldn’t ever need to come into force but also noted that if needed “it must be temporary.”

The U.K. leader added that ultimately the Irish question shouldn’t allow Brexit to fail.

“We cannot let this disagreement derail the prospects of a good deal and leave us with a no deal outcome that no one wants.”

Sterling rose against the dollar before May’s unscheduled speech on Monday but was largely unchanged after her comments.