ITV News Consumer Editor Chris Choi has the latest as the UK faces a wave of industrial action
Unions have said they will respond to life-threatening incidents - known as a category one call - when they strike on December 21 in a row over pay.
Industrial action is being coordinated across England and Wales by the GMB, Unison and Unite unions, after they accused the government of ignoring pleas for a decent wage rise.
Mr Barclay said officials plan to meet on Thursday to discuss coverage of category two callouts - which cover heart attacks, strokes, epilepsy and burns.
He told ITV News he hopes trade unions will cover category two calls "in their entirety," adding it would be a "hugely positive step".
It is 'important' emergency callouts are prioritised by trade unions when ambulance workers go on strike this month, Steve Barclay told ITV News
"We will clearly need to put in place contingency measures in terms of some of the ambulance calls, but we’re keen to engage constructively with trade union partners in terms of what they’re willing to cover during the period of the strike," he said.
He added that lower risk calls - including category three and four - would still be responded to, and that the government would put in place a range of contingency measures to ensure so.
Asked if contingency plans included bringing in the army to provide cover, Mr Barclay said it was "part of that discussion".
'We’ll put in place a range of contingency measures and obviously the army is part of that discussion'
Ambulance workers will strike a day after members of the Royal College of Nursing (RCN) stage their second walkout, also over pay.
According to the GMB, more than 10,000 ambulance workers across nine trusts in England and Wales will strike.
Members of the union will strike at:
South West Ambulance Service
South East Coast Ambulance Service
North West Ambulance Service
South Central Ambulance Service
North East Ambulance Service
East Midlands Ambulance Service
West Midlands Ambulance Service
Welsh Ambulance Service
Yorkshire Ambulance Service.
GMB representatives are set to meet individual trusts to discuss requirements for life-and-limb cover.
How will the strikes by ambulance workers and other NHS staff work?
Paramedics, emergency care assistants, call handlers and other staff will also walk out on December 28.
Unite general secretary Sharon Graham said: "The fundamental cause of the crisis in the NHS is massive understaffing, because workers are leaving the NHS in droves due to low pay and impossible workloads.
"Steve Barclay just doesn’t seem to get it. The first stage strategy to tackle the crisis involves creating a decent pay structure by making a decent pay offer. Otherwise, the staff exodus continues and the crisis deepens.
"On average every health worker’s real pay is worth some 20% less than it was in 2010. A porter’s pay is down 21% in real value and a nurse’s pay down 26%.
"It seems as one commentator said recently the NHS staff are too important to strike, but not important enough to get a decent wage."
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