Boris Johnson says the “reality” of Brexit is there will need to be customs checks on the island of Ireland after the UK leaves the European Union (EU).
But the Prime Minister (PM) rejected claims that would effectively mean a hard border, in the form of a series of customs posts set five or 10 miles back.
He told BBC Radio 4’s Today programme: “A sovereign united country must have a single customs territory.”
He refused to give details, but said formal proposals would be made soon.
Speaking in the Commons on Tuesday, Brexit Minister James Duddridge said the government would “set out more detail on an alternative to the backstop in the coming days”.
He also said he wanted to “assure the House there will be no infrastructure checks or controls at the border”.
The UK is set to leave the EU on October 31.
Mr Johnson has said the exit will go ahead with or without a deal – despite Members of Parliament (MPs) passing a law last month forcing him to ask for an extension from the EU if Parliament hasn’t voted in favour of a specific deal or leaving without one.
The issue of the Irish border – and how to keep it free from border checks when it becomes the frontier between the UK and the EU – has been a key sticking point in Brexit negotiations.
The current government says the solution reached by the EU and Theresa May, the backstop, is unacceptable and an alternative to it must be found.
Mr Johnson was speaking at the start of the third day of the Conservative Party conference in Manchester where ministers have made a raft of policy announcements, including raising the National Living Wage.
But the plans have been overshadowed by allegations that Mr Johnson squeezed the thigh of journalist Charlotte Edwards under a table at a lunch in 1999.
Asked about the accusation, the PM told BBC Breakfast it was “not true”, but it was “inevitable” he would face “shot and shell” because of his stance on Brexit.
According to leaked proposals, the government has accepted there must be customs checks on the island of Ireland, but they would be conducted away from the border – mostly where goods originate or at their final destination. -BBC