The European Union’s refusal to renegotiate the Brexit deal governing Northern Ireland has put the bloc on a fresh collision course with the U.K., as Boris Johnson’s government warns it will suspend parts of the agreement if the EU doesn’t budge.

David Frost, the U.K. minister for EU affairs, on Wednesday called on the bloc to rip and substantially rewrite the controversial Northern Ireland Protocol, the part of the U.K.’s separation agreement that governs trade and market rules for the region. The EU declined.

"Respecting international legal obligations is of paramount importance,” European Commission Vice President Maros Sefcovic said in a statement on Wednesday. "We will not agree to a renegotiation.”