DHL drivers in the West Midlands and North West are to be balloted for strike action over pay.
The drivers, who deliver parts and cars to and from JLR sites, have not had a pay offer for this year, Unite said. Their annual pay rise, usually implemented every January, has not gone ahead.
Drivers on JLR contracts in Birmingham, Wolverhampton, Solihull and Widnes in Cheshire are to be balloted.
Up to 300 DHL JLR Solihull logistics workers have already voted in favour of industrial action, the union said. DHL said it was disappointed by the ballot and remained open to constructive discussions.
"DHL is an extremely profitable company, so there is no justification for its failure to present a fair offer," Unite general secretary Sharon Graham said.
"These workers have Unite's full backing in ensuring DHL put forward an acceptable deal."
The union said industrial action would cause severe disruption to JLR's UK operations.
Strike dates in Solihull will be announced by workers in the coming days.
"DHL will be fully accountable for any disruption to JLR if it continues delaying a fair pay offer," Unite regional officer Melvyn Palmer said.
"Industrial action can still be avoided, but that will require DHL to present a deal our members are willing to accept."
A DHL Supply Chain spokesperson said: "We are disappointed that Unite the union has announced its intention to ballot HGV drivers on one of our automotive contracts, and we regret that Unite members based at our Logistics Operation Centre in Solihull have voted in favour of industrial action.
"We remain open to constructive discussions and are committed to reaching a resolution for all parties that recognises the contribution of our colleagues, while protecting the long-term competitiveness of the operation."