BRUSSELS, June 9 (Xinhua) -- The European Union (EU) respect Britain's decision to leave the union and will implement it, but if the two sides want to construct a new relationship, they need more realism about what is and is not possible, Michel Barnier, EU's chief Brexit negotiator, has said.

Commenting on this week's Brexit talk in Brussels, Barnier said on Friday that progress has been made over the past days on a certain number of subjects linked to the orderly withdrawal, which can be resolved before the next European Council in June.

However, "there is a lot of work to be done on the three other separation issues," including the protection of the personal data of EU citizens, protection of geographical indications and the infringement and administrative procedures concerning Britain which will be ongoing at the end of the transition, he noted.

In addition, divergences on the governance of the Withdrawal Agreement and the issue of Ireland and Northern Ireland remain large, he added.

Stressing the importance of a regulatory alignment, the chief negotiator reaffirmed that "it is in Northern Ireland's interest to keep the same rules in these areas, and to avoid new barriers to the daily exchanges on the island."

In the meantime, concerning Britain's newly released customs paper, which the EU received Thursday, Barnier said he personally welcomed the publication of this paper, which raised more specific questions.

On whether it is workable solution to avoid a hard border, the paper doesn't give a specific solution for the regulatory alignment to avoid a hard border, said Barnier.

As to whether Britain respects the integrity of the Single Market and the Customs Union, Barnier called on more clarity from Britain.

"The UK wants to continue benefiting from our free trade agreements. Does that mean that we will have to reopen, renegotiate or even re-ratify our existing agreements in order to keep the UK in our customs territory after the transition?" said Barnier, further noting that the paper should be an all-weather backstop.

"Let me be clear: our backstop cannot be extended to the whole UK... because it has been designed for the specific situation of Northern Ireland," said Barnier.

Barnier's Friday speech was widely seen as "pouring cold water" on Britain's UK-wide, time-limited backstop proposal.

Clearly enraged by the potential of Northern Ireland being left in alignment with the EU while the rest of Britain isn't, prominent Brexiteer Nigel Farage called on British Prime Minister Theresa May to be tougher in her negotiating stance.

"Barnier is trying to break up the United Kingdom," he was quoted by the Express as saying.