The European Union (EU) will not discuss anything with Britain about a future post-Brexit relationship until issues relating to the Irish border are resolved, Michel Barnier has said.
Mr Barnier said the backstop is the “only solution we have found to maintain the status quo on the island of Ireland”.
During a highly curtailed press conference with Taoiseach Leo Varadkar in Dublin, he said: “We would not discuss anything with the UK [on future relations] until there is an agreement for Ireland and Northern Ireland, as well as for citizens' rights and the financial settlement."
Mr Barnier was in Ireland ahead of a meeting of EU foreign ministers in Luxembourg and an emergency summit of EU leaders in Brussels on Wednesday.
On what was his fifth visit to Dublin as EU Brexit negotiator, Mr Barnier held meetings with Mr Varadkar, Tánaiste Simon Coveney and Finance Minister Paschal Donohoe.
He said it is the intention of the EU to protect the status of the Good Friday Agreement while also protecting the integrity of the single market.
“It is not an easy task, but I am confident we will find operational solutions, whatever happens, the EU will stand fully behind Ireland. The EU will stand fully behind Ireland,” he said.
Mr Barnier also said that the political declaration on the future UK-EU relationship "can be [amended] extremely quickly”.
“We want to respect the UK's parliamentary debate, the House of Commons is trying to decide how it sees its future relationship with the EU. We all hope that these talks will produce a positive outcome. We can be much more ambitious about a future relationship,” he said.
Mr Barnier's comments echoed expressions of solidarity made to Varadkar last week in his meetings with German Chancellor Angela Merkel and French President Emmanuel Macron, both of whom May will travel to meet on Tuesday.
Mr Varadkar spoke of the necessity of avoiding border in a no-deal: "I know the European Commission and other EU member states fully understand these issues, and are supportive and constructive about finding a way forward should a no-deal arise. But, it will be a shared challenge."
He said he and Mr Barnier exchanged views about the length of a possible extension to Brexit.
“I will be speaking to some (fellow EU leaders) on the phone today and tomorrow. There will, of course, be different views but I am confident that we will reach an agreement,” he said
He added by saying he "sincerely hopes it will be possible to build sufficient consensus in Westminster to ratify the withdrawal agreement.”
Our job is to make sure Irish interests are understood and protected and that commitments made on no hardening of the border are honoured - @MaryLouMcDonald tells @SkyNews pic.twitter.com/rbwlG9Cow5— Sinn Féin (@sinnfeinireland) April 8, 2019
Meanwhile, Sinn Féin president, Mary Lou McDonald, warned that a customs union does not "solve the problem for the north of Ireland" as she visited Westminster for Brexit talks with Jeremy Corbyn.
She noted that a customs union "probably makes sense for Britain" but said: "You need to be aware that membership of the customs union alone does not solve the problem for the north of Ireland - we need alignment also with the single market.
"These are the bare minimums that are required just to keep the lights on our island. I think for our purposes we have to be clear that this Brexit saga cannot go on indefinitely - there actually has to be a conclusion, there has to be an endpoint.
"Whether there is a deal, and I hope there is, or no-deal, I hope that that doesn't come to pass, but irrespective of whether there's a deal or no-deal or an extension of any duration we are very clear, and the British political system needs to be very clear, that the commitments made to Ireland must be honoured."
Chief Negotiator for Brexit Michel Barnier has vowed that the European Union will stand behind Ireland whatever the outcome of Brexit may be.
Mr Barnier said he was delighted to back in Dublin for his fifth visit as Chief Negotiator, after meeting with the Taoiseach, Tánaiste Simon Coveney and Finance Minister Paschal Donohoe:
"The aim of our meetings today, first and foremost, was to take stock of the latest developments in London and discuss Wednesday's European council in Brussels as convened by Donald Tusk."
We are ready to make this clearer about the customs union if needed and this can be done very quickly says @MichelBarnier.. but insists EU stands fully behind Ireland, backstop is the only deal on table #Brexit #iestaff pic.twitter.com/H7vaUJMzMe— McConnellDaniel (@McConnellDaniel) April 8, 2019
The discussions that took place today were largely focused on what would happen in Ireland in a potential no-deal scenario.
"There have been intensive discussions between our teams over the past weeks. Our goal is to protect the Good Friday Agreement, peace on this island, and integrity of the single market. It is not an easy task but I am confident that we will find operational solutions.
"The EU will stand fully behind Ireland. You have our full support. The backstop is currently the only solution we have found to maintain the status quo on the island of Ireland."
Taoiseach Leo Varadkar said : "We discussed the developments in the United Kingdom, including the cross party talks now underway, Prime Minister May's request and the assurances that she provides us in her letter.
"We both welcomed the Prime Minister's statement, that the Withdrawal Agreement, which includes a protocol on Ireland and the backstop, is not up for renegotiation and that the cross party discussions are focusing on the future relationship.
"The EU has always said that should the UK change its red lines, that we should be prepared to amend the political declaration on the future relationship."
Mr Varadkar expressed awareness that the UK and Northern Ireland will hold European Parliament elections if it is not out of the EU by May 22.
"From Ireland's perspective, we're open to extending the deadline to allow time for these discussions to run their course and come to a conclusion."
Mr Varadkar said that a no-deal Brexit would be damaging for everyone.
"However, given the ongoing uncertainty, we need to continue our preparations for a no-deal and that's exactly what we're doing."
Ahead of this week’s European Council meeting, the Taoiseach has also spoken by phone with Prime Minister Rutte of the Netherlands, Prime Minister Bettel of Luxembourg, and Prime Minister Muscat of Malta.
The Taoiseach also had a phone call with Prime Minister May this evening, who spoke about her recent letter to Donald Tusk seeking an extension of the Article 50 deadline, and her ongoing preparations for the Summit on Wednesday.
Additional reporting by Digital Desk