Prime Minister Theresa May is expected to propose a transitional period after Brexit takes effect in March 2019 and offer to settle EU demands for Britain's "divorce bill" in a key speech in Florence on Friday.
British media said May will offer a two-year transition, including a commitment to meet post-Brexit payments for that period, at an estimated cost of at least 20 billion euros (24 billion dollars) over two years.
May's office said she will "discuss a vision for a bold new economic and security partnership and set out the prime minister's plan for a time-limited implementation period, offering certainty and clarity to businesses and citizens."
"The eyes of the world are on us but if we can be imaginative and creative about the way we establish this new relationship ... I believe we can be optimistic about the future we can build for the United Kingdom and for the European Union," May was quoted as saying in advance remarks from her speech.
May chaired a special cabinet meeting on Thursday to discuss her much-anticipated speech, as critics warned that divisions in her Conservative government could make any new pledges largely symbolic.
In a sign of unity, Foreign Secretary Boris Johnson, Chancellor of the Exchequer Philip Hammond and other cabinet members are expected to be in Florence to watch May's speech.
The BBC said May was likely to rule out both a Canadian-style free-trade deal with the EU after Brexit and a Norwegian-style agreement for Britain to join the European Economic Area while accepting unrestricted freedom of movement.
