Paramedics in north-west England have vowed to take strike action "every week" as a row over pay rumbles on.
North West Ambulance Service staff who are members of the GMB union said they would walk out "until at least October" unless a resolution is found.
The GMB said it was because staff are "desperate for management to listen to their side of the story".
NWAS said it was "frustrated" at the union's "unwillingness" to join conciliatory talks.
Ambulance staff across the region - which covers Lancashire, Cumbria, Cheshire, Merseyside and Greater Manchester - plan to walk out for a 26-hour period every weekend, from 28 July "until at least October", the GMB said.
NWAS paramedics have already staged four strikes in recent weeks.
'Enough is enough'
GMB organiser Mike Buoey said it was because they have "been waiting a long time for their job to be re-evaluated for the years between 2005 to 2016".
He added: "After more than 13 years, our members are now saying enough is enough."
NWAS said paramedics who are not members of GMB and emergency medical technicians will be working as normal, though there may be delays in reaching some patients.
Lisa Ward, interim director of organisational development for NWAS said: "The trust is extremely disappointed.
"We are moving forward with a meeting which our other two unions, Unison and Unite, have agreed to attend but are frustrated at GMB's unwillingness to accept our invitation and engage with us.
"The invitation to join the trust, our other trade unions and the National Job Evaluation Group remains open to the GMB."