British Prime Minister Theresa May has been given 24 hours to come up with a plan to pull the UK out of the current political crisis or face a no-deal Brexit.
European leaders, including Tanaiste Simon Coveney, ramped up pressure on Mrs May to come up with a "detailed plan of action" on how the UK can end the Brexit turmoil that has paralysed Westminster.
While the EU has repeatedly insisted it does not want to see Britain leave without a deal, Mr Coveney warned: "People would be very foolish to assume this is some kind of political game and that an extension will automatically be facilitated."
Another senior government source said: "There is growing frustration in Europe across the EU capitals. Nobody wants another year of this."
With the possibility of another vote on the divorce deal still unclear due to parliamentary rules that have been invoked in Westminster, Mrs May is expected to write to EU leaders in Brussels outlining what type of Brexit extension she wants.
The bloc has said a request would need to be made ahead of tomorrow's summit to allow the EU 27 to consider it.
Downing Street was last night considering its options ahead of a key 48 hours for Brexit, but as turmoil persists, the prime minister has branded the current stalemate a "political crisis", a spokesman said.
A short extension until the end of June is almost certain to be sought, which would give Mrs May breathing space to try to revive her deal, which has already been rejected twice by MPs.
Europe's chief negotiator, Michel Barnier, set out the test that Europe expects Mrs May to meet if it is to grant an extension, warning: "We cannot prolong uncertainty without having a good reason for it."
He also cautioned that a long extension would need a reset of Britain's Brexit approach.
"A longer extension needs to be linked to something new, there needs to be a new event, a new political process," he said.
Mr Barnier also moved to increase pressure on the UK over the threat of a no-deal Brexit, telling reporters: "Voting against no-deal does not prevent it from happening.
"Everyone should now finalise all preparations for a no-deal scenario. On the EU side, we are prepared."
The readiness of the bloc to cope with the shock of a cliff-edge Brexit was also made clear in Dublin following a meeting between EU council president Donald Tusk and Taoiseach Leo Varadkar.
"Preparations continue in Ireland and across the European Union for a no-deal scenario, which would have serious consequences for all concerned," a government spokesperson said.
As the latest developments were being digested in Brussels, the Tanaiste held a series of meetings there with key figures in the Brexit process, including his British counterpart David Lidington.
On a visit to Dublin, European Council president Donald Tusk expressed EU solidarity with Ireland amid Brexit talks.
Taoiseach Leo Varadkar welcomed Mr Tusk in front of the media, but neither man made any reply when questioned by journalists.