The new strike dates will heap more pressure on Britain's state-funded National Health Service (NHS) which is already stretched by staff shortages and record backlogs.

British Prime Minister Rishi Sunak told reporters he was disappointed about the disruption caused by strikes, adding that he was trying to "make the right long-term decisions for the country for everybody's benefit."

The Royal College of Nursing (RCN) said thousands of its members would strike again on Jan. 18 and 19 over pay after walking out on two days in December.

"I do not wish to prolong this dispute but the Prime Minister has left us with no choice," RCN General Secretary Pat Cullen said on Friday.

Strike dates for the nurses union's members in Scotland are also expected to be announced in the new year after they voted to reject a pay offer from the Scottish government this week.

Ambulance workers represented by the GMB union scheduled a new date for action on Jan. 11 after suspending another walk out later this month.

"People across the country have been wonderful in backing us and we care so much about them too. That's why we are suspending the proposed GMB industrial action on the 28th December," GMB National Secretary Rachel Harrison said.

Health minister Steve Barclay said unions had announced co-ordinated strikes in January "to cause maximum disruption at a time when the NHS is already under extreme pressure".

Barclay noted that ambulance staff on picket lines had raised concerns about working conditions, and he said it was important to use the extra time to keep talking about how to make the NHS a better place to work.