Prime Minister Theresa May will set out five “tests” for a future UK-EU deal and pledge to “bring our country together” in a major speech on Friday.
The “deepest possible” free trade deal is achievable because it is in both EU and UK interests, she will argue.
She is expected to set out details of how the UK will seek to mirror EU rules in some areas and “diverge” in others.
A cabinet minister said she will also stress the UK “can’t get everything we want” from Brexit talks.
Transport Secretary and leading Brexiteer Chris Grayling told BBC Radio 4’s Today programme Mrs May “will recognise it is not about cherry-picking”.
He said there would be “an awful lot of detail about how things would work” and Mrs May would set out a “very clear picture” of a post-Brexit economic relationship between the UK and EU.
Labour’s Shadow Brexit Secretary Sir Keir Starmer said he wanted to see “specifics”: “We’ve had vague assertions and we’ve had red lines and we’ve had sound bites and now we really need concrete answers.”
He said she “must deal with” how she plans to avoid a hard Irish border, after she said earlier this week that an EU proposal for a “common regulatory area” on the island of Ireland was unacceptable.
“I agree with her, it’s simply not a road that we can go down but that really ramps up the pressure on her to say what then is the answer,” Sir Keir said.
Scotland’s First Minister Nicola Sturgeon said on Twitter the PM’s speech “must set out exactly how she intends to achieve her – seemingly contradictory and unachievable if we leave single market/customs union – objectives” and the time for “vacuous, meaningless rhetoric” was “long gone”.
The UK is due to leave the EU on 29 March 2019 but it wants a transition period lasting around two years after that, intended to smooth the way to the future post-Brexit relationship between the UK and the EU.
BBC assistant political editor Norman Smith said Mrs May was expected to “reach out” to the EU in the speech as part of a bid to get it to at least begin serious talks about a future trading relationship.
Mrs May’s speech has been relocated from Newcastle to the Mansion House in central London, because of severe weather.
She will pledge to bring the country back together “taking into account the views of everyone who cares about this issue, from both sides of the debate”.