Ed Miliband “absolutely” sees a prime minister when he looks in the mirror in the morning reported BBC .
In an interview with BBC political editor Nick Robinson, the Labour leader admitted his “mettle had been tested” by reports that some Labour figures thought he should step down.
But he denied his leadership was a problem and said: “What doesn’t kill you makes you stronger.”
The Conservatives said Mr Miliband had not learned from “Labour’s mistakes”.
In a wide-ranging interview ahead of a speech at the University of London on Thursday, Mr Miliband said he was “not in the whingeing business” and that the pressure in his job was expected.
He added that “disunited parties are parties that the public worry about” and that the Labour Party would “go forward… united”.
The BBC’s Nick Robinson says the speech will inevitably be termed a “fight-back”.
In it Mr Miliband will say that Labour’s economic plans will be delivered through “big reform” rather than “big spending”.
“We will be the wealth creators, not just the wealth distributors; the devolvers of power, not the centralisers, and the reformers of the state, not the defenders of it.”
A major theme will be the “zero-zero economy”, which he said was about “people asking why they are on zero-hours contracts while those at the top get away with zero tax”.