Many Geneva airport ground staff will strike Sunday over a labour dispute with their employer, the Dubai National Air Travel Agency (Dnata), their union said, in a move expected to slow holiday traffic.

Dnata personnel, who reportedly handle about a quarter of the traffic through Geneva's Cointrin airport, will begin their strike at 4:00 am (0300 GMT) on Sunday, the SSP public sector union said on X, formerly Twitter.

The planned work stoppage will surely slow traffic amid the busy Christmas rush, with some 60,000 passengers reportedly expected to travel through the airport on Sunday.

Dnata staff handle various ground operations, including ticketing services and baggage handling, for a number of international airlines, including British Airways, Air France and KLM.

The union, which has been threatening the strike since early in the week, said the duration of the stoppage would be evaluated "hour by hour", according to the 20minutes online news site.

Workers are demanding that Dnata, an Emirati airport service provider, hike salaries by five percent.

They also want the company to provide a premium for some physically challenging jobs and additional pay for night and Sunday work, something Dnata has refused to do, union representative Jamshid Pouranpir told 20minutes.

Dnata has offered to raise salaries by three percent, and has also agreed to drop a controversial plan to cut contributions to staff retirement funds, but that has not been enough to satisfy the workers.

Dnata representative Alexandre Koenig told 20minutes that the company remained "determined to find an agreement", but said it would consider any work stoppage to be "disproportionate" and "illegal".

SSP meanwhile decried "pressures" exerted by the company, alleging that it has threatened to fire employees who strike, the news site reported.