Austria's Chancellor Sebastian Kurz arrives at a European Union leaders summit in Brussels, Belgium December 13, 2018. REUTERS/Francois Lenoir

BRUSSELS (Reuters) - EU leaders agreed on Thursday to spell out that the “backstop” guarantee to avoid a hard border between Ireland and Northern Ireland should only be a temporary solution, Austrian Chancellor Sebastian Kurz said.

Kurz said the leaders had heard British Prime Minister Theresa May express concerns that the backstop could potentially apply indefinitely.

“In the session afterwards we defined two things, firstly that the withdrawal agreement cannot be re-opened and re-negotiated and secondly stipulated and made clear that the so-called backstop, the ruling for Northern Ireland should be temporary and not permanent,” he told reporters.