Taoiseach Leo Varadkar is to hold talks with the British Prime Minister Theresa May in Dublin on Wednesday.

The leaders will meet ahead of a European Council summit on Thursday.

It comes as Mrs May has been holding talks the German Chancellor Angela Merkel and Dutch Prime Minister Mark Rutte on Tuesday to discuss "clear concerns" over the UK's Brexit withdrawal agreement.

She is meeting EU leaders in an attempt to "seek reassurances" on the Irish border backstop.

Speaking in Brussels on Tuesday evening, Mrs May said: "The backstop is a necessary guarantee for the people of Northern Ireland - and whatever outcome you want, whatever relationship you want with Europe in the future, there's no deal available that doesn't have the backstop within it.

"But we don't want the backstop to be used, and if it is we want to be certain that it is only temporary.

"And it's those assurances that I will be seeking from fellow leaders over the coming days."

British Prime Minister Theresa May (left) is greeted by European Commission President Jean-Claude Juncker at EU headquarters in Brussels | Image: Francisco Seco/AP/Press Association Images

Mrs May added that her government is preparing for a no-deal scenario.

"We have already stepped up the no-deal preparations, that has been happening in recent days."

A planned House of Commons vote on the agreement for Tuesday was scrapped, as Mrs May admitted on Monday that it would not be passed by MPs there.

It remains unclear when Westminster will now vote on the agreement - but it is likely to be January at the earliest.

 However attempts by Mrs May to win concessions from EU leaders looks unlikely.

The European Commission President Jean-Claude Juncker has warned that there is "no room whatsoever for renegotiation of the Brexit withdrawal agreement.

"The deal we have achieved is the best deal possible - it is the only deal possible," he said.

"There is no room whatsoever for renegotiation."

German Chancellor Angela Merkel (left) greets British Prime Minister Theresa May upon her arrival at the Chancellery in Berlin, Germany | Image: NurPhoto/SIPA USA/PA Images

European Council President Donald Tusk has also warned that the deal cannot be renegotiated - but said officials are "ready to discuss how to facilitate UK ratification."

He said Brexit had been added to the agenda of this week's two-day summit in Brussels.

I have decided to call #EUCO on #Brexit (Art. 50) on Thursday. We will not renegotiate the deal, including the backstop, but we are ready to discuss how to facilitate UK ratification. As time is running out, we will also discuss our preparedness for a no-deal scenario.

— Donald Tusk (@eucopresident) December 10, 2018

While Tánaiste Simon Coveney said Ireland remains hopeful that a deal can be reached - but said that in the meantime the country must prepare for a no deal Brexit on March 29th.

"We are now stepping up, not only preparations but actions to actually respond to that potential reality," he said.

He said the EU may be able to offer Mrs May a statement of clarification on the Irish border "that may offer the reassurance needed in Westminster" - but warned that the agreement itself could not be renegotiated.

He said any declaration must be consistent with the legal text which protects the peace process and the integrity of the EU Single Market and Customs Union.

And speaking on Monday, Taoiseach Leo Varadkar said the backstop cannot be changed - noting that the withdrawal agreement had taken nearly two years to negotiate and has "the support of 28 member states."

"It is not possible to open up any one aspect of this without opening up all aspects of the agreement," he said.

All this as the UK Labour Party has indicated it will wait to see what Mrs May returns from her trip to Europe with before announcing its next move.

A spokesperson for the party said that if she returns to the UK without significant changes, she will have "decisively and unquestionably lost the confidence of parliament on the most important issue facing the country."

The party will then decide whether to table a motion of no confidence in her leadership.

Additional reporting: Jack Quann