BRUSSELS • Britain may be leaving the European Union, but it will still have to settle the divorce bill in euros, not pounds, according to an EU document on the upcoming negotiations.

The document did not say how much the Brexit settlement might cost, but EU officials previously said it could be as much as €60 billion (S$89.8 billion), sparking howls of outrage in London, which puts the figure closer to €20 billion.

"An orderly withdrawal of the United Kingdom from the union requires settling the financial obligations undertaken before the withdrawal date," according to the European Commission document.

"The agreement should define the precise way in which these obligations will be calculated... the obligations should be defined in euro," it said.

The document was drawn up for the European Commission, which will conduct the Brexit negotiations with Britain.

It covers in more detail the same grounds outlined last month by European Council president Donald Tusk, in response to British Prime Minister Theresa May's official March 29 notification that Britain was leaving the bloc.

Both the divorce bill and the fate of EU citizens are expected to be among the toughest areas to reach an agreement on, following a Brexit campaign that rallied against immigration and Britain's payments to Brussels.

For disputes outside EU law, "an alternative dispute settlement should only be envisaged if it offers equivalent guarantees of independence and impartiality as the European Court of Justice", it said.

AGENCE FRANCE-PRESSE