Boris Johnson has admitted it could take longer than two years for the United Kingdom to sign a trade deal with the European Union.
The foreign secretary said today “electoral considerations” in France and Germany could lead to a delay.
Theresa May has said a free trade deal with Brussels can be completed alongside the two-year exit talks.
She is expected to trigger Article 50 - the formal process of leaving the EU - at some point this month.
But Johnson issued note of caution today when asked if a deal would take two years.
“It depends how our friends and partners choose to handle it,” he told the British Chambers of Commerce (BCC) annual conference.
“They can play it long, they have electoral considerations, as everybody knows. I think there’s every reason why we [should] go this full tilt and get it done within two years. But let’s see how it goes.”
The prime minister has said no deal with Brussels on trade is better than a “bad deal”.
But George Osborne warned the same conference today that leaving the EU without a trade deal would be “the biggest act of protectionism in British history.”
David Davis also told ministers today to be prepared for the possibility the UK would not be able to agree a Brexit deal with Brussels.
A Downing Street spokesman said the Brexit secretary had told Cabinet to prepare for the “unlikely scenario in which no mutually satisfactory agreement” was reached.
In his speech, Johnson took aim at Sir John Major - who yesterday accused the government of being over-optimistic about Brexit.
He did not mention the former Tory prime minister by name, but said: “I get a bit impatient when I hear people droning and moaning about the state of state of the world.
“And I hear them warn that the sky is about to fall on our heads ... and I feel like saying, ‘Come off it, sunshine.’
The foreign secretary added: “Every generation hears its prognostications of gloom. And look at us today. We are living longer than ever before.”