Foreign Secretary Jeremy Hunt has said a no-deal Brexit “would be a mistake we would regret for generations”, after a working tour of northern Europe.
But he said he believed that other countries wanted to “engage seriously” to try to get a “pragmatic outcome”.
He also told ITV News he did not rule out the UK accepting EU environmental and social legislation, in order to help get a free trade deal.
It comes as Brexit talks resumed in Brussels between UK and EU officials.
There has been growing speculation about the possibility of the UK leaving the European Union without a deal in March 2019.
Bank of England governor Mark Carney said this month the possibility of the UK and EU failing to reach agreement on the terms of departure was “uncomfortably high”.
He was criticised as “the high priest of Project Fear” by Tory MP Jacob Rees-Mogg, who leads the Tory pro-Brexit European Research Group.
International Trade Secretary Liam Fox, a leading Brexiteer, has put the chance of failing to come to an agreement at “60-40”, blaming the “intransigence” of the European Commission.
Mr Hunt told ITV he believed the government’s plan was the “framework on which I believe the ultimate deal will be based”.
But he said, although the UK must be “prepared for all outcomes”, if the UK were to leave without a negotiated deal: “It would be a mistake we would regret for generations, if we were to see a fissure, if we had a messy, ugly divorce.
“Inevitably that would change British attitudes towards Europe.”
He also said it was his job as foreign secretary to tell other governments that “the implications of not getting a deal are profound in terms of our friendship and co-operation with foreign countries across a whole range of areas”.
Asked if the UK would consider EU proposals that the UK should accept EU environmental and social legislation he said: “I think we have to see what their proposal was, some of those things can have an impact on the level playing field, some won’t.”
The government has been touting its plans for Brexit agreed in July at Chequers – the prime minister’s country residence in Buckinghamshire – to the EU and its leaders, including the French President Emmanuel Macron, whom Theresa May met at his summer retreat.
But the EU’s chief negotiator Michel Barnier appeared to rule out a key UK proposal – allowing the UK to collect EU customs duties on its behalf – in July.
Liam Fox said earlier this month: “It’s up to the EU27 to determine whether they want the EU Commission’s ideological purity to be maintained at the expense of their real economies.”
Brexit talks resumed in Brussels this week between UK and EU officials, focused on the Irish border – a key sticking point – and future relations.
A European Commission spokesman said: “As this week’s round is at technical level there won’t be a meeting between Michel Barnier and Dominic Raab.
“We will confirm in due course whether a subsequent meeting has been arranged.”