A strike by thousands of junior doctors is looking increasingly likely as last-ditch talks continue to avoid a walkout.
Health Secretary Jeremy Hunt is poised to make a statement in the House of Commons at 3.30pm on Monday on the issue.
Three days of talks between the British Medical Association (BMA), Government officials and NHS Employers - hosted by the Advisory, Conciliation and Arbitration Service (Acas) - have so far ended without resolution.
Doctors are poised to take action on three days over pay and working conditions, providing emergency care only for 24 hours from 8am on Tuesday followed by full walkouts from 8am to 5pm on December 8 and 16.
The action would cause mass disruption to the NHS, with hospitals forced to cancel outpatient clinics and non-urgent operations.
In its guide to safe picketing for the strike action, the BMA said: "It is likely that our armed forces colleagues will be asked to step in to provide support for clinical services on the days of action.
"The law does not permit them to take part in industrial action but their support for services during the industrial action is welcome."
Health Secretary Jeremy Hunt previously refused to agree to discussions unless BMA officials came to the negotiating table first, but changed his mind on Wednesday when he told BMA chairman Dr Mark Porter "any talks are better than strikes".
A BMA spokeswoman said: "Strike action is still planned for Tuesday and talks will carry on on Monday."
Some 98% of more than 37,000 doctors balloted by the BMA voted in favour of strikes.
A new contract is set to be imposed from next summer on doctors working up to consultant level.
Mr Hunt previously tried to avert strikes with a fresh deal, including an 11% rise in basic pay.
This is offset by plans to cut the number of hours on a weekend that junior doctors can claim extra pay for "unsocial" hours.
Currently, 7pm to 7am Monday to Friday and the whole of Saturday and Sunday attract a premium rate of pay.
Under the new plans, a higher rate would run from 10pm to 7am Monday to Friday, and from 7pm on Saturday evenings - a concession on the previous 10pm.
Mr Hunt argues that, under the new deal, just 1% of doctors would lose pay and those would be limited to doctors working too many hours already.
The BMA has said the increase in basic pay is misleading due to the changes to pay for unsocial hours. It also has other concerns over flexible pay plans for some specialities.
Downing Street confirmed Mr Hunt will update Parliament on the situation in an oral statement to the House of Commons.
Number 10 said the statement would give MPs the latest information on the Government's contingency plans for the planned strike as well as ongoing contract negotiations through Acas.
Asked if David Cameron had a message for NHS patients ahead of the strike, a Downing Street spokesman said: "The negotiations and discussions are still continuing. They continue today at Acas.
"Clearly, we would want those discussions to come to a conclusion where the strike is called off. That's always been our objective."
Other NHS staff are being urged to join picket lines set to be mounted outside hospitals from 8am on Tuesday.
Rehana Azam, national officer of the GMB union, said "It is very disappointing that Jeremy Hunt has not entered into meaningful dialogue with the junior doctors who are now forced to take industrial action with a heavy heart to defend their terms and conditions of employment.
"GMB is encouraging members to show support for the junior doctors on the picket lines. We want them to attend in their own time with flags and banners, and I know that they will back this call.
"The junior doctors are now at the forefront of resisting further cuts to pay and conditions in the health service. Since the start of the recession in 2008 the pay of NHS staff has fallen by 10% in real terms. The Chancellor now wants another five years of pay restraint.
"These cuts in pay have already led to staff shortages in the ambulance service and things will only get worse. That is why we need to get behind the junior doctors in this dispute."