Ambulance staff in the West country may strike over Christmas in a dispute involving pay and conditions.
Talks are ongoing to avert the ambulance drivers' strike
Unison members employed by the Great West Ambulance Service are considering limited strike action.
Further action is believed to be planned on New Year's Eve and New Year's Day.
Staff are thought to be considering a four-hour strike on December 24 and 25 following a dispute between Unison and the trust over pay and conditions.
The Great Western Ambulance Service provides emergency cover for Gloucestershire, Wiltshire and the former county of Avon.
The trust urged the public not to panic and said contingency plans would be put in place.
A spokeswoman for Great Western Ambulance Service said: "We remain committed to resolving any dispute with our unions promptly and openly.
"We are therefore deeply disappointed that despite constructive, face-to-face talks with Unison where agreement was reached on seven out of the 10 issues raised, that the union intends to carry out strike action."
Unison said any decision to go on strike had not yet been finalised.
A Unison spokeswoman said: "Talks of a strike are premature. We are in urgent talks to avoid industrial action."