FILE PHOTO: A road which crosses the border from County Donegal in Ireland to County Londonderry in Northern Ireland, is seen from near the border village of Lenamore, Ireland, February 1, 2018. REUTERS/Clodagh Kilcoyne/File Photo

There can be no changes to the Irish “backstop”, an arrangement to avoid a hard border between European Union member Ireland and British-ruled Northern Ireland after Brexit, Estonian President Kersti Kaljulaid told Reuters.

Many British lawmakers, especially in Prime Minister Theresa May’s governing Conservative Party, fear the backstop will trap the UK in a permanent customs union with the EU after Brexit.

They are withholding support for the Brexit deal negotiated between May and the EU, raising the prospect Britain will leave the bloc on March 29 without an orderly transition arrangement in place – something that could disrupt trade and other ties.

Ireland and the rest of the EU say there is no credible alternative to the backstop, which would prevent customs and other checks having to be conducted after Brexit on the border between the Irish republic and Northern Ireland.

The removal of a hard border was a key element of restoring peace to the island of Ireland after decades of conflict.

Asked about British demands to change the backstop, Kaljulaid, whose country joined the EU in 2004, told Reuters at the Munich Security Conference: “This is not possible.”

Asked if a time limit could be put on the backstop, she added: “Then it is not a backstop any more. We agreed that there will be an Irish backstop. It can’t be changed.”

Kaljulaid nonetheless said she was concerned about Britain leaving the EU without reaching a deal with the bloc.

“We are all concerned … A no deal Brexit – if it will happen- will be a huge problem. It would be terribly difficult administratively,” she said.