LONDON/BRUSSELS (Reuters) - Britain expressed confidence on Friday that no hard border with Ireland would return following Brexit, but European Union negotiators have dismissed a proposal by Britain on how to ensure goods would flow freely after it quits the EU.

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At a negotiating session on Wednesday, Brussels officials and diplomats said the EU rejected proposals London first made last summer and introduced into the talks last month. That verdict reflected no change in the positions but put a more formal gloss on the impasse.

A British suggestion that it could form a “customs partnership” with the EU, collecting duties on behalf of the EU while pursuing its own tariff policy and refusing to be bound by EU courts and regulations, was dismissed last year in Brussels as impractical and a threat to the EU market.

That opinion was confirmed on Wednesday to Olly Robbins, who runs Britain’s negotiating team, EU officials and diplomats said. One described the British idea as “rather farcical”.

Both sides have committed to avoiding customs checks and other border impediments that might rekindle violence in the British province of Northern Ireland.

The EU has said Britain should be ready to leave Northern Ireland under EU economic regulations if it wants a treaty to ensure an orderly withdrawal next March. British Prime Minister Theresa May rejects that because it could isolate the province from the mainland.

British officials did not comment on the substance of London’s latest proposal. EU diplomats said it was designed to resolve the Irish border issue by avoiding customs checks between Britain and the EU, while keeping Britain out of the EU’s customs union -- something May has also rejected despite pressure from some in her own party.

A spokesman for May said he did not “recognize” reports of the EU rejecting London’s proposal, adding: “We are confident that in the coming months, if all sides work together productively, we can achieve a solution to the Ireland/Northern Ireland border that works for everyone involved.”

EU and British negotiators have also begun discussions on how their post-Brexit relationship should look, with the aim of agreeing a joint political declaration on the shape of future trading terms alongside a withdrawal treaty later this year.

They are due to hold four further rounds of talks on the Irish border and on the future relationship before EU leaders meet to review progress at a summit at the end of June. The next talks in Brussels will be in the first week of May.

One EU diplomat said London still appeared determined to secure an open-borders trade deal that would apply to the whole of the United Kingdom so that Northern Ireland would not be left in a special position with the EU, different from the mainland.

That, however, was creating a problem, since EU leaders were determined not to allow Britain as a whole to have such a deal without accepting governance from Brussels, though they were willing to be more flexible in the case of Northern Ireland.