Theresa May is to deliver an address tonight as she prepares to meet EU leaders to discuss her request for a "short" delay to Brexit.
No 10 said the British Prime Minister will make a statement in Downing Street at 8.15pm after a series of meetings with opposition party leaders in Parliament.
Earlier, European Council president Donald Tusk said he believed a short delay "would be possible" after he spoke to the Mrs May following her formal request for an extension of the Article 50 withdrawal process to the end of June.
The British PM made the request in a letter to Mr Tusk exactly 1,000 days after the 2016 referendum which delivered a 52%-48% majority to quit the EU.
Initially Downing Street declined to comment on reports she would be making a statement but Taoiseach Leo Vardakar let the cat out of the bag.
Speaking in Dublin, he said: "That will be an opportunity for her to set out her plan, her timeline, as to how an extension would work."
We always said we'd be open to an extension if there was a purpose to it and I think it's important that we hear from her first and we'll respond as 27, as the European Union, in the next couple of days.
The leaders of the Labour Party, SNP, Liberal Democrats, Green Party, Plaid Cymru and the Independent Group are understood to have been invited to meetings with Mrs May.
Mr Tusk, a former Polish prime minister, told a press conference in Brussels: "In the light of the consultations that I have conducted over the past days, I believe that a short extension would be possible.
"But it would be conditional on a positive vote on the Withdrawal Agreement in the House of Commons.
"The question remains open as to the duration of such an extension."
Mr Tusk indicated that it should be possible for leaders of the remaining EU 27 to approve his plan at a summit in the Belgian capital starting tomorrow.
He said that while he did not foresee the need for another "extraordinary" summit next week, he would not hesitate to call one if necessary.
"If the leaders approve my recommendations and there is a positive vote in the House of Commons next week, we can finalise and formalise the decision on extension in the written procedure," he said.
"However, if there is such a need, I will not hesitate to invite the members of the European Council for a meeting to Brussels next week."
Mr Tusk added: "Even if the hope for final success may seem frail, even illusory, and although Brexit fatigue is increasingly visible and justified, we cannot give up seeking until the very last moment a positive solution - of course without opening up the Withdrawal Agreement.
"We have reacted with patience and goodwill to numerous turns of events and I am confident that also now we will not lack the same patience and goodwill at this most critical point in this process."
Earlier, during a stormy session of Prime Minister's Questions, Mrs May sparked speculation that she may step down if either MPs or Europe demand a longer extension to the Article 50 negotiation process.
"As Prime Minister, I am not prepared to delay Brexit any further than June 30," she said.
If the delay is approved by the EU leaders, Mrs May will rush legislation through both Houses of Parliament next week to remove the March 29 leaving date from Brexit laws.
She told MPs she intends to table her Withdrawal Agreement for a third time in the Commons, in the hope of overturning massive defeats inflicted on it in January and March.
Aides declined to name a date for the third "meaningful vote" - known in Westminster as MV3 - but said it would happen "as soon as possible".
Earlier European Commission president Jean-Claude Juncker warned the British PM that Brexit would have to be complete before May 23 or the UK would have to take part in elections to the European Parliament beginning that day.
Mrs May said involvement in the elections would be "unacceptable", but appears to regard the July 1 date when new MEPs will take their seats as the effective deadline.
Aides said Mrs May will "passionately" make her case for a three-month delay on Thursday to the leaders of the remaining 27 EU states, whose unanimous approval is required for any extension.
But an unconfirmed report in French news magazine Le Point suggested that President Emmanuel Macron will argue against any postponement beyond March 29.
Only six days ago, Mrs May's effective deputy David Lidington warned that a short delay would be "downright reckless". And a motion tabled by the Government last week appeared to keep a longer extension of nine months to a year on the table.
But Leave-backing ministers are understood to have piled on pressure at Tuesday's Cabinet meeting to keep any delay short.
Downing Street aides said the final form of Mrs May's letter to Mr Tusk was not decided until this morning.
Asked if the decision had the backing of Cabinet, a Number 10 source would say only: "There was a long discussion on Brexit at Cabinet yesterday."
In her letter to Mr Tusk, Mrs May said it remains the Government's policy to take the UK out of the EU "in an orderly manner" on the basis of the Withdrawal Agreement and Political Declaration agreed in November and supplemented by documents agreed with Mr Juncker last week.
The agreement was rejected by 230 votes in January and 149 votes earlier this month.
Commons Speaker John Bercow said on Monday he would not allow the same motion to be brought again during this session of Parliament, unless it was substantially changed.
But Mrs May told the Commons: "The Government intends to bring forward proposals for a third meaningful vote.
If that vote is passed, the extension will give the House time to consider the Withdrawal Agreement Bill. If not, the House will have to decide how to proceed.
Labour leader Jeremy Corbyn accused Mrs May of "running down the clock" on Brexit in.
He told the Commons: "This Government has led the country and themselves into crisis, chaos and division."
PA
