German chancellor Angela Merkel has said Boris Johnson has 30 days to come up with an alternative plan to replace the Irish backstop.
The pair met in Berlin today for Brexit talks, with the Prime Minister keen to find a way to maintain frictionless trade at the Northern Irish border.
Mr Johnson has previously written to European Council president Donald Tusk to say the UK would leave the EU without a deal unless the “anti-democratic” backstop was scrapped.
This request was rejected by Mr Tusk.
The backstop has been one of the major sticking points in Brexit negotiations – it is a contingency measure to prevent a hard border between Northern Ireland and the Republic of Ireland.
It would mean Britain would keep a close relationship with the EU for an indefinite period.
The backstop was part of Theresa May’s exit deal that was rejected three times by Parliament but the EU has insisted it will not reopen talks on the issue.
Mrs Merkel said the backstop had always been a "fallback position" and would only come into effect if no other solution could be agreed.
She said: "If one is able to solve this conundrum, if one finds this solution, we said we would probably find it in the next two years to come but we can also maybe find it in the next 30 days.”
Mr Johnson said the timetable was “blistering” but he was "more than happy" with it.
A Downing Street source said the government was happy with the tone of Mrs Merkel's exchange.