Junior doctors in England will stage two strikes and only deal with emergencies during a third day of action in December if they support industrial action in a ballot.
The British Medical Association (BMA) said it had taken the "extraordinary step" of announcing the proposed dates and type of action ahead of the ballot result on Wednesday.
If there is a yes vote, junior doctors will only provide emergency care for 24 hours from 8am on December 1, followed by full walkouts from 8am to 5pm on December 8 and 16.
Health Secretary Jeremy Hunt said threatening "extreme action" was "totally unwarranted" and would harm vulnerable patients.
The BMA is in dispute with the Government over new contracts.
In an email to all members in England, BMA council chairman Mark Porter said: "We are releasing this information at this early stage because we want to give as much notice as possible.
"It sounds like an oxymoron when talking about industrial action, but we genuinely want to minimise any disruption to other NHS staff and, above all, to patients.
"Our dispute is with the Government and our ballot for industrial action is a last resort in the face of their continued intransigence."
The union has refused to get back around the negotiating table with the Government in the row over a new contract, which is set to be imposed from next summer on doctors working up to consultant level.
Mr Hunt had made a bid to avert strikes with a fresh deal, including an 11% rise in basic pay and overtime pay after 7pm on Saturday evenings, a concession on the previous 10pm.
Flexible pay premiums would be applied to more specialities than just general practice and A&E care, with acute medical ward staff and psychiatrists benefiting, he said.
The Health Secretary argued that just 1% of doctors would lose pay because of the deal and those were limited to doctors working too many hours already.
He said maximum working hours per week would fall from 91 to 72 under the new deal.
After the proposed strikes were announced, Mr Hunt said: "Threatening extreme action is totally unwarranted and will harm vulnerable patients.
"Refusing to talk to a Government that wants to improve weekend care for patients and reduce doctors' hours can only damage the NHS.
"Rather than striking, the BMA should return to the negotiations they walked away from a year ago and put their patients first."
Johann Malawana, the BMA's junior doctor committee chairman, said the increase in basic pay was misleading as it would be "offset by changes to pay for unsocial hours - devaluing the vital work junior doctors do at evenings and weekends".
The BMA said it has told the Government it wants to work with it to agree a new contract, but it needs a number of concrete assurances.
These include withdrawal of the threat to impose the new contract, proper recognition of unsocial hours as premium time, no disadvantage for those working unsocial hours compared to the current system, and no disadvantage for those working less than full time and taking parental leave compared to the current system.
In his email, Dr Porter updated members on legal advice the BMA has obtained from labour relations expert John Hendy QC, following suggestions by an NHS trust that the proposed industrial action was in breach of the Trade Union Labour Relations (Consolidation) Act 1992.
"In short, it is counsel's opinion that the suggestions made by the trust are seriously misleading.
"The offence to which they have referred only applies when a doctor acts with malice towards the patient concerned and when he or she knows that the probable - not just possible - consequence of their action in breaching their employment contract would be the death or serious injury of the patient concerned.
"This is highly unlikely to apply to any doctor participating in the proposed industrial action. It is also worth noting that no prosecution of the sort suggested by the trust has ever been brought under the act.
"The unity of the profession, regardless of branch of practice or seniority, underlines the strength of feeling and solidarity in standing with our junior doctor colleagues in defence of patients and our working lives," he said.