DUBLIN (Reuters) - The European Union is ready to work again on the political declaration on future EU-UK ties but the Brexit withdrawal deal already agreed is the best one possible, the bloc’s chief negotiator, Michel Barnier, said on Monday.

European Union's chief Brexit negotiator Michel Barnier arrives to meet with Portugal's Prime Minister Antonio Costa at Sao Bento palace in Lisbon, Portugal January 17, 2019. REUTERS/Rafael Marchante

British Prime Minister Theresa May will try to break the Brexit deadlock in her own parliament on Monday by setting out proposals that are expected to focus on winning more concessions from the European Union.

Barnier has been consistent since May’s deal suffered a crushing defeat at home last week that the EU would consider a potential British request for closer post-Brexit ties, but will not renegotiate the withdrawal agreement rejected by parliament.

“The withdrawal agreement with all its dimensions, including the backstop, is the best deal possible,” Barnier told Ireland’s RTE in an interview after a 45-minute meeting with Irish Foreign Minister Simon Coveney in Brussels.

The ‘backstop’ is an insurance policy to ensure there is no return to border checks between EU member Ireland and the British province of Northern Ireland.

“As I see, following carefully the political debate in London, this debate is much more now on the future relationship. As I said last week at the EU parliament, if the UK want to be more ambitious, we are ready to be.”

“It is now for the UK leaders to build a stable and positive majority for a deal. We are waiting for the next steps from the UK government but we are ready to work again on the political declaration.”

May will focus on changing the ‘backstop’, which under the current withdrawal accord would come into force if Britain and the EU fail to reach a comprehensive trade deal at the end of a planned transition period.

The backstop is strongly opposed by many lawmakers in May’s Conservative Party and by the small Northern Irish party that props up her government as it could mean Northern Ireland diverging from the rest of the UK on regulatory matters.

Asked three times if there was any scope for further concessions on the backstop, Barnier reiterated that the withdrawal agreement - of which the backstop is a key element - was the best deal possible.