BRUSSELS (Reuters) - Britain could accept legally-binding assurances on the disputed Irish border backstop that would not require reopening of the EU-UK Brexit deal, diplomatic sources said, signalling a possible shift from Prime Minister Theresa May’s official line.

Britain's Secretary of State for Exiting the European Union Stephen Barclay is pictured outside the Houses of Parliament, in London, Britain, February 14, 2019. REUTERS/Hannah McKay

EU and British diplomatic sources told Reuters after talks earlier this week between Brexit Secretary Stephen Barclay and the bloc’s chief negotiator Michel Barnier, however, that London was still seeking changes to the backstop that the EU has already ruled out.

“Potentially those things can be achieved without changing the Withdrawal Agreement,” a British official said of the legal guarantees on the backstop that London was demanding.

“If they can get what they want through other means, they’ll accept that the Withdrawal Agreement will not be reopened,” one EU diplomat said of what was discussed during the Barnier-Barclay meeting.

“But they still want a time limit on the backstop or a unilateral exit,” another one said. “Barnier said ‘no’.”

Both sides are seeking a way out of the stalemate that has prevailed since British lawmakers last month overwhelmingly rejected the Brexit deal May had agreed with the EU last year.

May has since said she would seek changes to that deal to replace the backstop, which some Brexit supporters fear could leave Britain stuck with EU trade rules indefinitely.

The EU has refused to make changes in the legal withdrawal agreement for Britain, saying the backstop is needed as an insurance that no border controls could return between EU member state Ireland and the British province of Northern Ireland after Brexit, seen as a key to peace and prosperity on the island.

The bloc is offering to instead tweak the accompanying political declaration on future EU-UK ties and says controls on goods would largely not be needed on the sensitive Irish border should the UK decide to stay in the bloc’s customs union.

But May has ruled out staying in the EU’s customs union as it would undercut a key Brexit promise that Britain would be free to pursue its own trade deals around the world.

On Friday, Barclay was meeting ambassadors of EU states in London before travelling to Brussels on Monday together with the British Attorney General Geoffrey Cox for more talks with Barnier. May is also expected in Brussels next week.

The EU is ready to give London assurances over the backstop in the declaration on future ties or separate statements, EU diplomats and officials say, to unlock the ratification of their Brexit deal in the House of Commons.

The bloc has already produced two rounds of such additional documents in December and in January but they have fallen flat among British parliamentarians.

Sources in the EU’s political hub Brussels currently do not expect any Brexit breakthroughs until mid-March, when the risk of the most damaging no-deal Brexit would have grown further.

May stands accused by some critics at home of running the clock down to force her lawmakers into a choice between her deal, no-deal or no Brexit. The EU believes the talks would go right down to the wire with a March 21-22, make-or-break summit of the bloc’s national leaders.