Tour de France organisers are working feverishly in the shadows to find a new start date for cycling's biggest stage race after public gatherings were banned until mid-July in the latest extension of the French coronavirus lockdown.

Originally slated to start from Nice with a caravan of around 4 500 people on 27 June and arrive in Paris 19 July, there is no chance the event can go ahead as planned and organisers face a mammoth logistical task of rescheduling.

So far organisers Amoury Sports Organisation (AS0) have remained silent publicly, but several mayors of the French towns along the planned route say they have been consulted on the matter of the new date.

French President Emmanuel Macron said in a televised address Monday that a strict lockdown in France would continue until at least 11 May and public gatherings were banned until mid July.

Tour director Christian Prudhomme has said previously that riders would need two clear months after the lockdown ended to get ready for the race, which is no longer possible given the 11 May extension.

France's Minister of the Interior Christophe Castaner spelled out on Tuesday that ASO had to reschedule or cancel.

"It is up to the organiser to analyse their ability to organise it and reschedule it," Castaner said on French radio.

Speculations surrounds a possible late July start, or mid-August, or even a September race.

ASO's reorganisation task is massive for an event with 21 start towns, 21 finish lines and over 3 000km of route and 500 000 roadside fans per day.

"Social distancing on the roadside wouldn't be a problem, but in the start towns, at the finish line and in the VIP tents it certainly would," Belgian virologist Marc Van Ranst told Flemish tv station Sporza on Saturday.

Suggestions the tour could be held behind closed doors have been ruled out. Fans are a key element of the Tour which is synonymous with the holidays in France, with the party atmosphere popping as the caravan winds its way through the prettiest parts of the country.

"The Tour de France is 3 000km of smiles," ASO chief Christian Prudhomme has said in reference to the holiday roadside gatherings. "We won't run a Tour de France without the fans."

Macron's announcement may have caught the organisers short and many people in France were surprised when the mid-July ban was announced.

A late July start for the Tour could be considered too close to that ban on public gatherings while also running up against another problem. To be able to race 21 tough stages, the athletes need to be in peak condition, and would ideally need a one-week preparation race before it.

ASO own the Criterium du Dauphine eight-day race and had been hoping to use that jaunt through the Alps in late June or early July. But that event has been postponed.

A second obstacle would be hotels, which would normally expect to be fully booked in the first two weeks in August.

A mid-August start would see the finish in September, meaning a clash with the Vuelta a Espana.

The Tour could be staged in September, but would lose its own sense of identity by moving out of the holiday period.

There are only 176 riders on a Tour, but the whole event involves around 4 500 people with team staff, logistics, police and media all moving every day in a minor miracle of organisation.

Cancellation is the worst case scenario.

The "Grande Boucle", as the Tour is known in France, is the central economic pillar which supports the 22 professional teams on the roster for 2020.

"It's as simple as this. If the Tour does not take place, teams could disappear, riders and staff alike would find themselves unemployed," said Marc Madiot, the chief of top French outfit Groupama-FDJ.

The riders are also straining at the leash to race with 2018's Welsh Tour winner Geraint Thomas saying he was desperate for the race to go ahead.

"There are bigger and more important things to sort out first, but as soon as it's safe and ready to go, we (Ineos) would love it to happen," said the Ineos rider whose team-mates Chris Froome and Egan Bernal have both won the Tour themselves.

2019 Tour de France in numbers:

4 500 people (organisation, sports groups, media partners, publicity cars, service providers)

176 cyclists (22 teams of 8 riders)

450 staff members (sporting directors, assistants, mechanics etc)

On the roadside:

10-12 million spectators (60% male, 40% female; 80% percent French, 20% foreign)

7 hours per day of fans lining the course routes

92% percent of spectators come in numbers (4 to 5 per group on average)

Security:

250 independent law enforcement members (Republican Guard, anti-riot police and mobile gendarmes)

29 000 police officers, gendarmes and emergency service workers deployed along length of course

3 000 regional security agents

Organisation:

100 full-time employees at ASO (Amaury Sport Organisation) and 400 partners

Over 500 hotels reserved

180 lorries to transport supplies daily

Media:

2 000 accredited journalists and photographers

500 TV production crew members

90 TV and radio journalists in commentary stands

Publicity caravan:

160 party vehicles for 11km parade

600 people (480 parade workers, 120 logisticians and technicians)