Irish Prime Minister Leo Varadkar says Brexit is undermining Northern Ireland’s hard-won peace by pulling Catholic and Protestant communities apart. Varadkar said Saturday that “Brexit has undermined the Good Friday Agreement” — the 1998 peace deal that ended three decades of violence in Northern Ireland. Varadkar also told Ireland’s RTE radio that the U.K.’s impending departure from the European Union “is fraying relationships between Britain and Ireland.” Brexit negotiations have stalled over the issue of the border between EU member Ireland and the U.K.’s Northern Ireland. Both sides agree there must be no customs posts or barriers that could disrupt businesses and residents or undermine Northern Ireland’s peace. But they haven’t agreed on how to guarantee that — and Britain is due to leave the bloc on March 29, AP reports.