LONDON - Britain will not have agreed a figure with the European Union for its so called Brexit divorce bill by October, Brexit Secretary David Davis said on Tuesday.

The EU wants agreement on how the exit bill - to be paid in euros - will be calculated before talks can move on to Britain's future relationship with the bloc.

"We're going to talk it through very, very carefully, so at this stage we're not going to commit, there won't be a number by October or November, whenever it is," Davis told BBC radio.

Davis said any Brexit transition should be over by the date of the next British national election, due by May 2022, but was likely to last for about two years.

"It's got to be done by the election. I would say the most likely is something like two years, maybe a bit shorter," Davis said.

He did not give a definitive answer about whether the European Court of Justice be the arbiter during for an interim customs deal but said Britain would next week set out its proposals on post-Brexit international arbitration.