Theresa May has told the Cabinet that she will not agree a withdrawal deal with the EU “at any cost”.
The Prime Minister said any agreement will be dependent on an “acceptable” framework for future relations in areas like trade and security, which is expected to be covered in a separate political document.
At a weekly meeting in 10 Downing Street, senior ministers discussed proposals for a “review mechanism” to ensure that the UK is not stuck indefinitely in a possible backstop arrangement designed to avoid a hard border in Ireland.
Mrs May assured ministers that there would be another Cabinet before any agreement is settled, though her official spokesman said no extra meeting has yet been scheduled ahead of the regular weekly gathering next Tuesday.
"Don't be under any illusion, there remains a significant amount of work to do," the spokesman told reporters.
'A real point of divergence'
Prime Minister Theresa May with European Commission President Jean-Claude Juncker.
The EU's chief negotiator Michel Barnier said a breakthrough on the Irish border issue was not close.
"For now, we are still negotiating and I am not, as I am speaking to you this morning, able to tell you that we are close to reaching an agreement," he told Belgian broadcaster RTBF.
"There is still a real point of divergence on the way of guaranteeing peace in Ireland, that there are no borders in Ireland, while protecting the integrity of the single market."
Following the Cabinet meeting, Mrs May's spokesman said: "The Prime Minister said she was confident of reaching a deal. She said that, while the UK should aim to secure a withdrawal agreement as soon as possible, this would not be done at any cost.
"The Prime Minister said that, once agreement was reached on a withdrawal agreement, it remains the case that nothing is agreed until everything is agreed and it will be subject to securing an acceptable full future framework."
Irish Taoiseach Leo Varadkar told the Prime Minister on Monday that he was ready to consider a review mechanism as part of a "backstop" arrangement to keep the border with Northern Ireland open after Brexit.
But he made clear that he would not accept an arrangement which gave the UK unilateral powers to ditch the customs union without the agreement of Brussels.