LONDON (Reuters) - Britain says it is ready to move to the next phase of Brexit talks and set out details of the future relationship it wants with the European Union.

Opening rounds of talks with Brussels have made little headway, with EU negotiators demanding greater clarity from the British delegation. The EU has warned that an already-tight timetable could be delayed ahead of a scheduled March 2019 exit.

Britain is keen to start talking about its post-Brexit relationship with Europe, wary of the need to reassure anxious businesses, citizens and investors. But, Brussels has insisted that progress must be made on divorce arrangements first.

“We’ve been crystal clear that issues around our withdrawal and our future partnership are inextricably linked, and the negotiations so far have reinforced that view,” a source in Britain’s Brexit department said.

Britain said it was preparing to publish several papers, including plans for a new customs arrangement and a proposal on how to resolve the difficulties of a non-physical border between Ireland and Northern Ireland.

“These papers show we are ready to broaden out the negotiations,” the source said.

The next round of talks is due at the end of the month, with both sides looking for progress towards a solution to three of Brexit’s thorniest problems: how much Britain should pay to leave, what rights British and EU citizens will have, and how to manage a land border to the bloc in Ireland.

The decision to announce the publications indicates Britain’s desire to counter criticism from Brussels about its approach to the talks.

In July, EU officials said progress was difficult not because Britain had unacceptable demands, but because it had no position at all on many issues.

A British paper focused on “issues unique to Northern Ireland and Ireland” is expected ahead of the talks, but no further details of the proposal were provided on Sunday.

Separate papers would also address “Continuity in the availability of goods for the EU and the UK” and “Confidentiality and access to official documents”, the Brexit department said.

Eager to push talks past the opening divorce issues and on to the future trading and legal ties to the bloc, Britain also promised a series of “Future Partnership” papers in the run-up to October’s European Council.

The first will be a proposal for new customs arrangements.