Boris Johnson has said the chances of a Brexit deal are “touch and go” – having previously said the odds of a no-deal Brexit were “a million to one”.
In a BBC interview at the G7 summit in France, he said it “all depends on our EU friends and partners”.
When pressed on the chances, he said: “I think it’s going to be touch and go. But the important thing is to get ready to come out without a deal.”
Mr Johnson has repeatedly said the UK will leave the EU on 31 October.
Asked if people would still be able to get their medicine if there was a no-deal Brexit, the prime minister said: “That is certainly a guarantee that we can make.”
But he added: “I do not want at this stage to say there won’t be unforeseen difficulties.”
Mr Johnson has previously said the UK must leave on 31 October “deal or no deal”, but that the chances of a no-deal Brexit happening are a “million to one”.
Speaking at the G7 summit on Sunday, he said: “I think in the last few days there has been a dawning realisation in Brussels and other European capitals what the shape of the problem is for the UK.”
He said he was an “optimist” and thought the EU would understand there is an “opportunity to do a deal”.
The PM also said if there is no deal, the UK would keep a “very substantial” sum of the £39bn Theresa May had agreed to pay the EU in her withdrawal agreement.
The G7 summit – a get-together of most of the leaders of the world’s largest economies – comes with just over two months until the UK is scheduled to leave the EU at the end of October.
Mr Johnson wants to remove the Irish backstop from the agreement – a key Brexit sticking point – but the EU has consistently ruled this out.
On Sunday, the PM met President Donald Trump to discuss a trade deal between the UK and the US.
Mr Johnson said the US’s aim to strike a deal within a year was “going to be tight”, adding: “These [Americans] are tough guys.”