The Taoiseach has told Theresa May he is willing to consider proposals for a review clause in any backstop plans for the Irish border in the wake of Britain leaving the EU.
During a phone call between Leo Varadkar and the Prime Minister on Monday, Mr Varadkar said that the outcome of a review could not involve a unilateral decision to end the backstop.
A spokeswoman for the Irish Government said that both leaders emphasised their commitment to avoiding a hard border and the need for a legally-operable backstop.
"The (British) Prime Minister raised the possibility of a review mechanism for the backstop," the spokeswoman added.
"The Taoiseach indicated an openness to consider proposals for a review, provided that it was clear that the outcome of any such review could not involve a unilateral decision to end the backstop.
"He recalled the prior commitments made that the backstop must apply 'unless, and until' alternative arrangements are agreed.
They both expressed the hope that the negotiations could conclude in a satisfactory manner as soon as possible."
A Downing Street spokesman described Mrs May's conversation with Mr Varadkar as "constructive", adding: "They agreed that the intention was that the backstop should only be a temporary arrangement and that the best solution to the Northern Ireland border would be found by agreeing a future relationship between the UK and the EU."
The call came after Mr Varadkar dismissed the idea of a time-limited backstop, saying it would not be worth the paper it is written on.
Reports at the weekend that Brexit Secretary Dominic Raab has privately demanded the right to pull Britain out of the EU's proposed Irish backstop after just three months had been criticised by the Irish government.
Irish deputy prime minister Simon Coveney said that their position remains "consistent and clear" that a time-limited backstop will never be agreed to by Ireland or the EU.
Speaking on Monday morning, Mr Varadkar described the UK as a "divided kingdom", which he said has not helped the negotiation process.
"The UK in many ways is a divided kingdom, the people are split 50/50 over whether they want to leave the European Union or not," he said.
"The Cabinet seems divided, the Government seems divided, Parliament is divided, and that has made it very difficult to come to an agreement.
"I'd much prefer to have a united kingdom, a united country, to be our partner in these negotiations, but we don't, so we have to work through."
He said that the Irish Government was working hard to try to reach an agreement by the end of the year but added that it cannot countenance the idea of a three-month limit to the backstop agreement.