MADRID (Reuters) - The main hurdle in talks between Spain and Britain over Gibraltar’s post-Brexit status is keeping cross-border traffic fluid, Spanish Foreign Minister Arancha Gonzalez Laya said on Tuesday. Madrid and London are negotiating how to police the land border between Spain and Gibraltar, a British Overseas Territory on the southern tip of the Iberian peninsula, as it was excluded from the last-minute exit deal reached between Britain and the European Union last week. Spain has secured an exemption for about 8,500 cross-border workers from border controls even if no agreement on free movement is reached, Gonzalez Laya said in an interview with RNE radio station. She added her government seeks to keep traffic between Gibraltar and Spain fluid and avoid long lines of cars and trucks.