The Conservative leadership hopeful will use his first major foreign policy speech to urge Britain not to agree to an early withdrawal from Iraq or back major concessions by Israel in the Middle East, likening weakness in the face of extremism to the appeasement of Hitler in the 1930s.
His message was a direct counter to his rival David Davis, who has traded on his tough image as shadow Home Secretary, and came as his supporters ruled out any prospect of a "dream ticket" deal with the former chancellor Kenneth Clarke.
The former deputy prime minister Lord Heseltine backed a Clarke-Cameron leadership alliance, arguing that Mr Cameron would benefit from working alongside "the most popular Conservative around at the moment". On Monday Mr Clarke renewed speculation about his leadership ambitions by confessing he was mistaken in his backing for the euro.
But Mr Cameron's supporters dismissed the overture, claiming Mr Clarke would be eliminated from the race before the final run-off. They believe around 25 of Mr Clarke's backers in the parliamentary party will ultimately switch their support to Mr Cameron.
Mr Cameron will say today: "If only, some argue, we withdraw from Iraq, or Israel made massive concessions, then we would assuage jihadist anger. That argument, often advanced by well-meaning people, is as limited as the belief in the Thirties that by allowing Germany to remilitarise the Rhineland or take over the Sudetenland, we would satisfy Nazi ambitions.
"As we discovered in the 1930s, a willingness to cede ground and duck confrontation is interpreted as a fatal weakness. It can only provide an incentive to escalate the struggle against a foe who clearly lacks the stomach for the fight."
Mr Cameron will argue that a shared British belief in fairness under the rule of law should unite the nation against extremists, cautioning against a "protracted exercise" to define "Britishness".
He will make a series of detailed proposals for strengthening Britain's homeland security, despite an unwritten bar on leadership hopefuls straying on to the detailed portfolios of Shadow Cabinet colleagues.
However, Mr Cameron is understood to have consulted Mr Davis on the broad themes of his speech. Colleagues said it was important for him to give his views on an issue of crucial national importance.
The speech is the first in a series covering foreign affairs, public services and other issues in the run-up to the Conservative Party conference in October.
Sources said Mr Cameron wanted to outline his views and beliefs to the party beyond the confines of his education portfolio.
Friends of Mr Cameron ruled out a joint leadership bid with Mr Clarke, despite Lord Heseltine's claim on the BBC that the former chancellor stood "head and shoulders ahead of any other candidate". Lord Heseltine said: "I would have thought that [David Cameron] might welcome a period very close to the top where he would gain experience from a professional bruiser, which Ken is.
"My real interest is helping the Tories to win. I think Ken is capable of landing punches on this Government in a way I don't see anyone else being able to do."
Senior Conservatives believe Mr Davis remains the man to beat in the leadership ballot due at the end of the year, but say the race is nevertheless still wide open.Reuse content