There is no breakthrough yet on the thorny Irish border issue, Dublin has warned, hours ahead of key talks between British Prime Minister Theresa May and top EU officials aimed at achieving progress on Britain’s Brexit deal.

The Republic of Ireland is demanding safeguards from London that Brexit does not lead to a hardening of its border with Northern Ireland, which is part of the United Kingdom.

A peace deal between both sides rests in part on their common membership of the European Union.

The issue has emerged as the toughest of three areas in which the 27 remaining EU member states want to see sufficient progress before they start discussing post-Brexit trade relations with London.

Time is pressing, with Britain due to leave the EU in March 2019.

“There is still a way to go,” an Irish government official said early Monday, calling for “clarity” on the need to prevent the re-emergence of a border.

May is to meet European Commission President Jean-Claude Juncker over lunch in Brussels, and is due later for talks with European Council President Donald Tusk.

The EU set Monday as a deadline for progress if its leaders are to approve moving to the next phase of Brexit talks at a summit next week.

On Friday, Tusk promised Ireland a veto on progressing to trade talks if it is not satisfied with Britain’s safeguards on the Irish border issue.

Agreement must also be reached on two other issues: Britain’s outstanding financial contributions to the EU and citizens’ rights.

A European Commission source said a deal was “doable” on Monday, while warning that they were not there yet.

Before meeting May, Juncker is due to consult with top EU lawmakers, after the European Parliament warned last week that more progress was needed on citizens’ rights and the Irish border. The EU legislature has a say on the final Brexit deal.

Meanwhile, on the domestic front, May could come under more pressure from both pro-EU and pro-Brexit lawmakers in her Conservative Party as the debate on her EU withdrawal bill resumes on Monday.

The bill’s fourth day of scrutiny by parliament’s lower house could feature attempted amendments to require a vote on a financial settlement, while up to 15 Conservatives could try to block May’s plan to specify the date of Brexit, according to British media reports.