The EU said Monday that last week's Brexit agreement was a "deal between gentlemen" and not legally binding, but insisted that it had the full backing of the British government.
The comments came after Britain's Brexit minister David Davis caused a row with Ireland by suggesting that Friday's interim divorce deal was "more a statement of intent than it was a legally enforceable thing".
The deal agreed by British Prime Minister Theresa May and EU commission chief Jean-Claude Juncker set out Britain's divorce bill and the rights of expatriates, and also made guarantees on Ireland's sensitive border with the British province of Northern Ireland.
"Formally speaking, the joint report is not legally binding, because it is not yet the Article 50 withdrawal agreement," European Commission spokesman Margaritis Schinas said in reference to Friday's deal.
"But we see the joint report of Michel Barnier and David Davis as a deal between gentlemen," Schinas added, referring to the EU's chief negotiator.
If approved by EU leaders on Friday, the informal deal on the divorce terms -- part of the Brexit process under Article 50 of the EU's Lisbon Treaty -- will allow the two sides to move to talks about their future relationship, including trade.
"It is a clear understanding that it is fully backed and endorsed by the UK government," Schinas said of the Friday deal.
Juncker met with May in Brussels on Friday "to ascertain that this was precisely the case. They shook hands," Schinas said.
Dublin and Brussels were alarmed by Davis's comments on Sunday, which seemed to minimise the UK's commitment to the deal.
Davis also said Britain will not honour financial commitments agreed in last week's agreement if it fails to secure a future trade deal.