Doctors could strike for the first time since 1975 if the government does not rethink proposed changes to NHS pensions.
The British Medical Association (BMA) said it will ask NHS doctors across the UK whether they are willing to provide only urgent and emergency care for a 24-hour period.
Dr Hamish Meldrum, chairman of council at the BMA, said: "We're taking this step very reluctantly and only because the government will not engage with us to even try to find a fairer way forward.
Under the BMA's plans, patient safety would be the priority.
Doctors scheduled to be in work would go to their usual workplaces, and provide all emergency care and other care urgently needed, but would not undertake some duties that could safely be postponed, said the BMA.
The action would be likely to involve the postponement of routine operations and non-urgent outpatient appointments in hospitals.
GP practices would remain open and staffed so they could see patients in need of urgent attention, but routine, non-urgent appointments would not be available on the day of action.
A series of actions is being planned but the impact on patients of the day of action would be reviewed before a decision to proceed with further action was made.
In January, 84% of the 46,300 doctors and medical students who responded to a BMA survey rejected the government's pension changes, with more than six in 10 saying they were personally prepared to take industrial action.
BMA Chairman Meldrum added:
"NHS staff agreed to major changes to their pensions only four years ago. As a result, the scheme is delivering £2 billion to the Treasury each year and staff have taken on sole responsibility for covering increases in costs due to improvements in longevity in the future.
"Now the government wants to tear up a deal reached through genuine negotiation and impose these further, unnecessary changes.
"There is still time for the Government to rethink its plans, but if it does not, we have made a firm commitment that patient safety will be the over-riding priority.
"If we do go ahead, anyone whose condition required urgent or emergency care or investigation that day would be treated.
All doctors due to be in work would still be in their usual workplaces. We would aim to work with managers, and other NHS staff to try to ensure as much notice and information about what was happening on the day as possible."
The ballot is scheduled to open on May 14 and close on May 29.
BMA Council will make a decision on what to do next following the results of the ballot. Plans for the day of action will be further developed with doctors locally and following discussions with employers.
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The bitter dispute over public sector pension reforms remains unresolved more than a year after the Government first unveiled the proposals.
More than a million and a half public sector workers staged a one day strike last November and most unions have refused to sign up to new pension arrangements.
Thousands of teachers and lecturers went on strike yesterday and further nationwide action could be taken next month.
Industrial action by doctors would represent a huge escalation of the dispute.
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Health Minister Simon Burns said: "There is no justification for well-paid doctors to take industrial action.
"The first responsibility of all NHS staff must to be help patients. Industrial action is completely unacceptable because it would put patients at risk.
Our proposals mean doctors will continue to receive pensions that are among the highest in the public or private sectors. A doctor joining the new scheme after 2015 could expect a pension of around £68,000 per year at state retirement age.
"Pension reform is necessary because people are living longer, healthier lives. Our proposals are a fair deal for staff and taxpayers and make public service pensions affordable and sustainable.
"It is fair that higher earners pay greater contributions relative to those on lower and middle incomes. Lower earner members should not be footing the bill - that is why we have protected those on lower salaries."