The European Union says that the current agreement with the U.K. remains the "best and only way" to ensure an orderly Brexit, after British Prime Minister Theresa May vowed to try to overhaul the deal.
EU Council President Donald Tusk's office said that the "backstop" on the Irish border which Britain seeks to renegotiate is "not open for renegotiation."
May says Parliament has made its wishes clear and that she will now seek "legally binding" changes to the Brexit withdrawal agreement reached with the EU.
She spoke after British lawmakers voted to try to renegotiate the Brexit divorce agreement with the EU to remove a contentious Irish border measure.
The House of Commons voted 317 to 301 to seek to replace the Irish border "backstop" that keeps the border between Ireland and Northern Ireland free of checkpoints.
The EU did leave other options for negotiation open.
Tusk spokesman Preben Aamann said that "if the U.K.'s intention for the future partnership were to evolve, the EU would be prepared to reconsider its offer and adjust the content and the level of ambition of the political declaration," referring to the political text to complement the legal withdrawal agreement.