Theresa May is flying to Canada on Monday to lay the foundations for a post-Brexit trade deal amid a continuing furore over the Government's approach to EU withdrawal.
The Prime Minister was facing calls to sack Foreign Secretary Boris Johnson, who was branded a "backseat driver" by a Cabinet colleague after setting out his own vision for a hard Brexit just days before a major speech in which Mrs May is expected to offer compromise.
A new trade deal between the EU and Canada is due to come into effect on September 21, eliminating 98% of Canadian import duties, in what Downing Street describes as a "significant boon" for UK exporters.
But when Britain leaves the EU, it will fall out of the Comprehensive Economic and Trade Agreement (Ceta), which was championed by the UK and took seven years to negotiate.
Mrs May hopes to use Ceta as a model for a new bilateral arrangement between Britain and Canada to be introduced "swiftly" after Brexit.
Under the terms of its EU membership, the UK cannot seal a free trade agreement with an outside country before its departure, though it remains unclear whether this will be possible during the "transition period" expected to last two or three years after the official date of Brexit in March 2019.
The Prime Minister and her Canadian counterpart Justin Trudeau are expected to agree the establishment of a new joint working group, the 13th established by the UK since last year's referendum, to prepare the ground for a bilateral deal based on Ceta soon after Brexit.
Speaking ahead of her visit, Mrs May said that Canada and the UK form a "powerful union" when they work together on priorities like free trade.
"My visit to Canada is not only about recognising our past but also looking ahead to our bright future," she said.
"We are both countries with ambitions to lead on the world stage and progressive values that underpin those ambitions, values including the importance of free trade, and respect for international law.
"When we come together and work as one to project our shared values on the world stage, we form a powerful union."
Mrs May's visit risks being overshadowed by the row over Mr Johnson's 4,000-word essay, in which he said Britain should make no payments for access to the European single market after Brexit, and made no mention of the transitional period which the Prime Minister is now thought to favour.
His intervention, which saw him revive the claim, branded "misleading" by the official statistician, that £350 million a week could be freed up for the NHS by Brexit, was widely interpreted as the first shot in a leadership bid.
Home Secretary Amber Rudd accused Johnson of "backseat driving", while Scottish Tory leader Ruth Davidson criticised him for releasing his comments the day after a terror attack in London.
Liberal Democrat leader Sir Vince Cable said Mrs May's credibility would be "reduced to zero" if she failed to sack the Foreign Secretary on Monday.
But Mr Johnson insisted he was "all behind" the Prime Minister, and Mrs May's de facto deputy Damian Green said he would not be sacked for comments which he said were in line with the PM's own speeches on Europe.
A number of commercial deals are expected to be sealed during the one-day visit to Canada, during which the PM will take part in round-table talks with potential business investors in the UK.
These include the expansion of Vancouver-based social media company Hootsuite in London, the supply of Tesco's product range to 100 West Coast supermarkets by the end of this year, and a £34 million Turner and Townsend contract to oversee refurbishment of part of the Canadian Parliament.
Mrs May will also welcome the appointment of Brigg & Goole MP Andrew Percy as her trade envoy to Canada.
The UK-Canada bilateral trade relationship is worth £15.2 billion annually and Britain is the second-biggest destination for Canadian investment abroad, with £1.75 billion invested since March alone.
Mrs May said: "Canada and the United Kingdom have a long shared history.
"British and Canadian soldiers, sailors and airmen and women have fought and died alongside each other in the pursuit of freedom, including at the Battle of Britain, where 23 brave Canadian servicemen lost their lives.
"We have developed the institutions of Westminster democracy, personal rights, and the common law. And we celebrate together our shared monarchy, and close ties of family and friendship."
Mrs May was later in the week due to fly on to the United Nations General Assembly in New York, where she will hold talks with French president Emmanuel Macron on tackling terrorist and extremist propaganda on the internet.
Liberal Democrat Brexit spokesman Tom Brake said: "Theresa May is racking up air miles desperately trying to recreate what we have already.
"This copy-and-paste Brexit is a huge waste of time and resources.
"Can ministers point to a single country that has responded to their plea for new and improved trade deals?
"The Government is pointing to a boost in drinks and spirits exports, but we'll need to keep enough to drown our sorrows given their shambolic handling of Brexit."
Mrs May and Mr Trudeau are expected to discuss a trade dispute involving Canadian aerospace company Bombardier, which is a major employer in Belfast.
Boeing has complained about alleged dumping of the firm's C-Series jets in the US, in a case which could lead to substantial financial penalties if American trade authorities find against Bombardier.
The planes are part-built in Northern Ireland, where Bombardier is the largest manufacturing employer, and the case is particularly sensitive for Mrs May because of her reliance on the support of DUP MPs for a majority in the House of Commons.
The Prime Minister last week raised the case in a phone call with US President Donald Trump.
The row involves a 2016 order from US airline Delta for up to 125 C-Series planes, whose wings are built in Belfast.
Boeing alleges the planes are being sold for less than they cost to produce, thanks to subsidies from the Canadian and UK governments.
Mrs May is set to meet Mr Johnson in New York, where the Foreign Secretary is expected to be in the audience when she addresses the United Nations General Assembly on Wednesday.
Mr Johnson was at the UN on Monday, at the head of an advance party of British ministers, also including International Development Secretary Priti Patel, Foreign Office ministers Alistair Burt and Lord Ahmad and business minister Claire Perry.
On her return from New York, Mrs May travels to Florence, Italy, on Friday for a speech designed to break the Brexit deadlock.