Theresa May is to meet European Commission president Jean-Claude Juncker in Brussels on Thursday for further Brexit talks, the Commission's spokesman has said.
Announcing the meeting on Tuesday, spokesman Margaritis Schinas said the European Union is still waiting to hear what the Prime Minister plans to do on Brexit.
"The European Union's position is clear," Mr Schinas told a news conference. "We are expecting, waiting once again to hear what the Prime Minister has to tell us."
Mr Schinas also said that Mr Juncker will meet Irish Taoiseach Leo Varadkar in Brussels on Wednesday.
The announcement comes after Mrs May's Parliament told her to go back to Brussels and demand changes to the Brexit divorce deal she negotiated with the bloc.
Asked if Mrs May would present an alternative to the backstop at her meeting with Mr Juncker, Mr Schinas said: "Let's see how the meeting develops on Thursday."
He added the backstop was a "central piece" of the Withdrawal Agreement and of "fundamental importance" to addressing the issues around the Irish border.
On Tuesday, the Northern Irish party which props up the British government demanded that the EU replace the "toxic" Irish border backstop that Mrs May agreed.
Speaking ahead of a meeting with Mrs May, the Democratic Unionist Party's leader Arlene Foster said: "The current backstop is toxic to those of us living in Northern Ireland."
Mrs May will make a speech in Northern Ireland on Tuesday afternoon and will insist that she can secure a Commons majority for a deal that "commands broad support" in Northern Ireland.
She will use her speech to acknowledge that it is a "concerning time" but "we will find a way to deliver Brexit" that honours commitments including avoiding a hard border with Ireland.
Meanwhile in Westminster, the working group bringing together senior Eurosceptic and former Remain-supporting Tories will continue efforts to agree alternatives to the backstop.
Talks involving Conservatives including Brexiteers Iain Duncan Smith, Theresa Villiers, Steve Baker and Owen Paterson along with former Remainers Nicky Morgan and Damian Green will continue in Whitehall, chaired by Brexit Secretary Stephen Barclay.
The first meeting on Monday was described as "detailed and constructive" by the Brexit department.
But Brussels has previously declared its opposition to any attempt to reopen the Withdrawal Agreement, insisting the backstop was the "only operational solution" to the border question.
