LONDON, June 16 (Reuters) - Britain is keeping all options on the table as a response in a dispute with the European Union over part of their Brexit deal covering Northern Ireland, Brexit minister David Frost said on Wednesday, adding that talks were not making much progress. Prime Minister Boris Johnson has said he could trigger emergency measures in the Northern Ireland protocol after its implementation at the beginning of this year has seen disruption to trade between Britain and its province. "All options remain on the table as regards steps forwards. Obviously we would prefer to find negotiated ways forward if we can. If that"s not possible obviously ... other options remain on the table," Frost told a parliamentary committee.