Trade secretary Liam Fox has suggested that there can be no decision on what the Irish border will look like after Brexit until there is a final deal between the UK and Europe.
It comes as Ireland promised to "play tough" on its threats to veto trade talks unless it was offered guarantees that there would not be a hard border - something that could only happen if the UK or Northern Ireland remained in the customs union or Single Market.
Fox said the government did not want a hard border "but the UK is going to be leaving the customs union and the Single Market" he said, speaking to Sky News on a trade trip to New Zealand.
"We've always had exceptions for Ireland, whether its voting rights to residence in the UK, we've always accepted a certain asymmetry, and that will have to be a part of whatever agreement we come to with the European Union. But we can't get a final answer to the Irish question, until we get an idea of the end state."
He continued: "And until we get into discussions with the European Union on the end state, that will be very difficult."
And Fox signalled that the pace of negotiations needed to pick up. "We have to get there faster than at the present time," he warned.
But the Irish border has been identified by the EU's chief negotiator Michel Barnier as one of the crucial areas where the UK must show progress to move on to trade talks in the next fortnight.