Theresa May is to make a statement to MPs at 15:30 GMT amid reports Tuesday’s vote on her Brexit deal is being delayed.
That will be followed by a statement from Commons leader Andrea Leadsom – and then a statement from the Brexit secretary on Article 50.
Two cabinet sources have told the BBC’s Laura Kuenssberg Tuesday’s planned Brexit vote will be delayed.
There is not yet any official confirmation of the move.
Downing Street had been insisting the vote would go ahead, despite Mrs May being widely expected to lose it.
But a third Cabinet source has told the BBC the vote is “definitely off”.
The deal has been agreed with the EU – but it needs to be backed by the UK Parliament if the UK is to leave the EU on 29 March with plans in place for a future relationship and the rights of EU citizens in the UK – and UK citizens in the EU – guaranteed.
Mrs May is thought to be trying to convince MPs to back her deal by suggesting the Northern Ireland backstop – the main item they object to – could be modified.
She has also been speaking to EU leaders about re-opening the withdrawal agreement, something both sides have previously ruled out.
It comes as the European Court of Justice ruled the UK can cancel Brexit without the permission of the other 27 EU members.
European Commission spokeswoman Mina Andreeva said the EU would not renegotiate the Withdrawal Agreement.
In a press briefing, she said: “We take note of the Court of Justice judgment today on the irrevocability of Article 50.
“We have an agreement on the table which was endorsed by the European Council in its Article 50 format on 25 November.
“As President Juncker said, this deal is the best and only deal possible. We will not renegotiate – our position has therefore not changed and as far as we are concerned the United Kingdom is leaving the European Union on 29 March, 2019.”
The pound fell 0.4% against the US dollar to $1.26, following reports the Brexit vote would be delayed. Against the euro, the pound was down 0.6% at 1.10 euro.
Dozens of Conservative MPs had been planning to join forces with Labour, the SNP, the Lib Dems and the DUP to vote down Mrs May’s deal.
Labour leader Jeremy Corbyn, who was hoping to use a defeat for Mrs May on Tuesday to force a general election, said: “The government has decided Theresa May’s Brexit deal is so disastrous that it has taken the desperate step of delaying its own vote at the eleventh hour.
“We have known for at least two weeks that Theresa May’s worst-of-all-worlds deal was going to be rejected by Parliament because it is damaging for Britain.
“Instead, she ploughed ahead when she should have gone back to Brussels to renegotiate or called an election so the public could elect a new government that could do so.
“We don’t have a functioning government. While Theresa May continues to botch Brexit, our public services are at breaking point and our communities suffer from dire under-investment.”
Labour MP Chris Leslie suggested his party could table a no-confidence motion in the prime minister on Tuesday.
But Conservative Brexiteer Peter Bone said Tory MPs would back her in such a vote – as would the Democratic Unionist Party, which is against her deal but is committed to keeping her in power.
Mr Bone said “every day that goes by” takes the UK closer to leaving the EU on World Trade Organization terms, without a deal – something he backs.
But he added: “Maybe there is a chance to renegotiate and I hope she will.”
Conservative Remainer Anna Soubry said on Twitter: “I gravely fear we are putting off the inevitable.”