LONDON, July 22 (Reuters) - British Business Secretary Kwasi Kwarteng said on Thursday the European Union had been inflexible over renegotiating the Northern Ireland part of the Brexit divorce accord and cautioned Brussels that it was not a deal that would last for ever. "A deal is a deal but it wasn"t something that was going to last forever," Kwarteng told Sky. "It was something that was flexible and we want to make it work more smoothly." "Article 16 ... it is something that we could do, to suspend it, we"ve chosen not to do that, that"s not our opening position and we want to be able to negotiate and have a conversation with the EU about how best to go forward." Britain demanded on Wednesday that the EU agree to rewrite the Northern Ireland protocol which covers post-Brexit trade involving the province just a year after it was agreed. The EU immediately rejected that call, saying Britain needed to respect its international obligations and pointed out it had been negotiated by Prime Minister Boris Johnson. read more The protocol was a key part of the Brexit settlement, backed by Johnson, that finally sealed Britain"s divorce from the EU four years after voters backed leaving in a referendum. Businesses in Northern Ireland say it is damaging trade, and some pro-British groups have protested at what they say is a weakening of ties with Britain, raising concerns about a return to the violence which plagued the province for three decades. The protocol addresses the biggest conundrum of the divorce: how to ensure the delicate peace brought to the province by a U.S.-brokered 1998 peace accord - by maintaining an open border - without opening a back door through neighbouring Ireland to the EU"s single market of 450 million people.