The Health Secretary has sought to calm a row with junior doctors, insisting the new contract is not about saving money or imposing longer hours.
In a letter to the junior doctors' leader at the British Medical Association (BMA), Jeremy Hunt said he could provide assurances about the Government's approach to the contract.
He said he was "saddened" by the distress being caused to doctors who "were misled by the calculator on the BMA website into believing that their pay will be cut by 30%".
Under the current plans, the contract will reclassify doctors' normal working week to include Saturdays and up to 10pm every night of the week except Sunday.
Medics argue they will lose out financially as evenings and Saturdays will be paid at the standard rate rather than a higher rate.
In his letter, Mr Hunt told Dr Johann Malawana he was "not seeking to save any money from the junior doctors' pay bill".
He said: "Whilst I want to see an end to automatic annual increments (with pay rises instead based on moving through the stages of training and taking on more responsibility), these changes would be cost neutral, rather than cost saving."
Mr Hunt said junior doctors would still benefit from four or five pay rises as they moved through their training.
While doctors would face an increase in those hours classed as a normal working week, this would be backed up by an increase in basic pay.
Mr Hunt said there would be a move to paying for hours worked, with additional pay for unsocial hours.
"Within this, I can give an assurance that nights and Sundays will continue to attract unsocial hours payments. I would be pleased to discuss in negotiations how far plain time working extends on Saturdays."
Mr Hunt also offered an "absolute guarantee to junior doctors that this contract will not impose longer hours".
He said: "No junior doctor working full-time will be expected to work on average more than 48 hours a week."
While NHS trusts could still pay for extra hours, they would have a duty to ensure this was only in exceptional circumstances.
Mr Hunt said the contract would be developed "to ensure that the great majority of junior doctors are at least as well paid as they would be now."
However, he said that "in any scenario, I can give an absolute guarantee that average pay for juniors will not reduce".