The Prime Minister will warn that the outcome of September's referendum remains "up in the air" and pledge to do "whatever it takes" to win.
But in a significant move, he will also use a speech at the Olympic Park in London to call on those outside Scotland to back "Team GB".
Last night, Deputy First Minister Nicola Sturgeon accused the Prime Minister of a "tawdry bid" to politicise a sporting event.
She also attacked him for speaking in England not Scotland, saying he did not have the "guts" to take on First Minister Alex Salmond.
The speech is part of a new, Canadian-style phase of the No campaign. Pro-Union parties believe appeals from other parts of Canada were crucial to the narrow victory in the 1995 Quebec independence referendum.
Last month, The Herald revealed that English celebrities have been signed up to 'lovebomb' Scots and urge them to stay part of the UK.
Mr Cameron is expected to say: "For me, the best thing about the Olympics wasn't the winning. It was the red, the white, the blue. It was the summer that patriotism came out of the shadows and into the sun. Everyone cheering as one for Team GB. And it's Team GB I want to talk about today. Our United Kingdom."
While the decision lies with four million Scots, 63 million people could be "profoundly affected", he will say.
And he will implore the English, Welsh and Northern Irish "let the message ring out. We want you to stay."
The Tory leader will also admit that the rest of the UK would be diminished without Scotland.
Ms Sturgeon accused the Mr Cameron of double standards over his choice of venue.
The First Minister was accused of politicising the Games last year after he dubbed Scotland's Olympic athletes 'Scolympians'.
Ms Sturgeon said: "Unfortunately, with this tawdry bid to use the Olympic Games - past and present - as a political tool, David Cameron has exposed the utter hypocrisy and double standards at the heart of the No campaign."
Yesterday, the Prime Minister faced calls for a change of tack on the referendum from one of his most senior backbenchers.
Andrew Tyrie, the Commons Treasury Committee chairman, called on the Chancellor George Osborne to rule out a currency union with an independent Scotland. Until now, ministers have stopped short, saying only that a deal would be "highly unlikely".
No 10 said last night that it did not intend to "pre-negotiate" before September's vote.
Mr Tyrie's intervention came during a Commons debate on Scotland which featured impassioned speeches from MPs of all parties. Tory MP Rory Stewart, who has announced plans for a 100,000-strong human chain along Hadrian's Wall this summer, said his message to Scotland was "I love you".
l Bagpipes gave soldiers - in a largely English unit - the courage to cross no man's land in Bosnia, a former United Nations commander said. Former colonel Bob Stewart, Tory MP for Beckenham, said he used two pipers frequently, with one of them able to calm intense fighting.