She has repeatedly said no deal is better than a bad one, insisting Britain must be prepared to walk away from the negotiating table.
May, who plans to take Britain out of the European Union's tariff-free single market, has said Brexit will allow Britain to seek bilateral trade deals with "old friends and new allies" and has created a new government department exclusively focused on trade.
Whatever happens on Thursday, the election campaign has not gone well for May, who has damaged her reputation with a series of gaffes and U-turns.
London police arrested 12 people in the Barking district of east London in connection with the attack and raids were continuing there, the force said.
Mrs May was asked whether she would recognise those who helped in the Manchester and London attacks in the Birthday or Christmas honours, but said "we never talk about those things".
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Survation polled 1,103 United Kingdom residents aged 18 and over by telephone on June 2 and 3 - the poll was carried out before the terror attack on London Bridge in which seven people were killed and 48 injured.
London police chief Cressida Dick said that, while some of the recent attacks in Britain had global dimensions, they had a largely domestic "centre of gravity".
On the face of it, this should be solid ground for the Prime Minister: as Home Secretary, the job she held until last summer, she cast herself as an authoritarian, an image she reinforced on Sunday morning, in the wake of the latest attack, when she sent a warning to extremists that "enough is enough".
The election was called in the aftermath of a seismic constitutional event - Britain's exit from the European Union. The police response to the rampage, which saw officers shoot dead the attackers within eight minutes of police receiving the first call, has been widely praised. And that's going to need a lot of police time.
He sought to defend the Government's record, saying the Tories had increased the number of armed officers and plan to boost funding for intelligence services by £500 million.
He sidestepped questions on how he had opposed 90-day detention of suspects in Parliament, adding: "Of course there are measures that I have not supported myself but the vast majority of measures that have come before the House of Commons I have supported...but Jeremy Corbyn has opposed every single one".
"Cutting police numbers is the most sure way of keeping us less safe".