French public sector trade unionists have warned they will not provide red carpets during the visit of Britain's King Charles III to Paris next week, but non-striking workers are expected to roll them out.

The CGT union representing staff at the National Furniture service, which is responsible for manufacturing and maintaining red carpets among other items, said Wednesday they would strike during the sovereign's trip to France from Sunday.

The union said its members would no longer provide "furnishings, red carpets or flag services."

"We’re aware that the king of England will be welcomed in France this weekend and our services will be required," a statement said, adding that the visit would take place "without us".

"We ask our managers to point out to the ministry of culture that any request for furnishings will be seen immediately by workers as a provocation," the statement added.

But a spokesman for the National Furniture service told AFP that only 24 members of staff were on strike on Thursday out of 420.

"The red carpet has been delivered and the trade unions have assured us that they will not block the work of non-striking staff," Loic Turpin said.

Charles III and his wife Queen Consort Camilla are expected to arrive in France on Sunday for their first official trip abroad since Charles ascended to the throne last September.

But the country is in the grip of fierce protests and strikes over President Emmanuel Macron's pensions reform, meaning the king's schedule is still being worked out.

Officials on both sides are concerned that protesters will use the occasion to publicise their fight against Macron's bid to increase the retirement age to 64 from 62 at present.

But in London, Prime Minister Rishi Sunak's spokesman told reporters Downing Street was "not aware of any plans to change the plan" concerning the king's visit.

The British monarch had been expected to attend a ceremony with Macron on Monday at the Arc de Triomphe before visiting the presidential palace and then the Senate.

He is also scheduled to be a guest of honour for a state banquet at the Palace of Versailles outside Paris on Monday evening, although the BFM news channel reported that organisers are thinking of switching the venue for security reasons.

Red carpets would be expected at each of these stops.

The schedule for Charles' trip to Bordeaux in southwest France on Tuesday is also up in the air, with trade unionists threatening to block a planned tram journey amid ongoing protests in the city.