Brexit Secretary David Davis said Sunday Britain will not honour financial commitments agreed this week with the European Union if they fail to secure a future trade deal, contradicting finance minister Philip Hammond.

"No deal means that we won't be paying the money," he told the BBC.

"It is conditional on an outcome. It is conditional on getting an implementation period, it is conditional on a trade outcome," he said.

"It has been made clear by number 10 already. So that's not actually new," Davis added, referring to the Downing Street office and residence of British Prime Minister Theresa May.

Under an initial agreement reached with the EU on Friday, Britain will pay a financial settlement of between £35 billion-£39 billion (40-45 billion euros, $47-52 billion) for leaving the bloc in March 2019.

The 15-page document, detailing post-Brexit arrangements for citizens' rights and the Irish border, was hammered out after nearly six months of negotiations and now allows the talks to move on to a future trade deal.

Davis' stance contradicts comments from Hammond on Wednesday, who said London would pay the bill regardless of their outcome.

"Nothing is agreed until everything is agreed in this negotiation," he told a parliamentary committee.

"But I find it inconceivable that we as a nation would be walking away from an obligation that we recognised as an obligation," he said.

"That is not a credible scenario. That is not the kind of country we are. Frankly, it would not make us a credible partner for future international agreements."

A spokeswoman for the Treasury reached Sunday declined to comment on Davis' remarks.