Troops are being trained to drive ambulances ahead of strikes as the government holds emergency COBRA meetings to limit disruption while 10 different industries go on strike this week.
Over the weekend, government sources said a decision had not yet been made to put in a formal request to the Ministry of Defence but said a decision was "not far off".
But the Cabinet Office has now confirmed military personnel are being deployed to NHS hospital trusts across the UK to "familiarise themselves with vehicles" ahead of ambulance strikes planned for 21 and 28 December.
Two emergency COBRA meetings will also be held this week as ministers step up plans to limit disruption caused by industrial action, which is set to take place every day until the end of the year.
Cabinet Office minister Oliver Dowden will lead a meeting with his department on Monday to help "protect the public" against a lack of service caused by the strikes.
Starting from Monday, 10 sectors are set to strike this week: rail, the NHS, the Eurostar, buses, National Highways, baggage handlers, Royal Mail, nurses, driving examiners and civil servants.
NHS workers who are Unison members in Northern Ireland will kick off this week's strikes.
Nurses in England, Wales and Northern Ireland, who are members of the Royal College of Nursing, will go on strike for the first time ever on Thursday and again on 20 December.
Union bosses have said the strikes could still be called off if the government sits down and tries to resolve all the different disagreements over pay and conditions.
Foreign Secretary James Cleverly told Sky News on Sunday unions should negotiate with the independent pay review bodies, not with ministers.
RMT rail union leader Mick Lynch requested an urgent meeting with Rishi Sunak.
The prime minister's spokesman said: "The government has played its part by facilitating a fair and decent offer and the RMT and its members should vote this deal through and end this harmful disruption."
Unison said the government has the power to halt the strikes by making an effort to "put a proper pay plan on the table".
"Instead of putting plans in place for the strike days, ministers should be concentrating all their efforts on ending the disputes," Sara Gorton, head of health at Unison, said.
"Speaking to unions about improving wages can work wonders as the Scottish government has found. It's time ministers in Westminster did the same. They should stop talking tough, put a proper pay plan on the table and get the unions in to discuss it."