Doubts continue to grow around this year's Tour de France after the UCI announced it was extending the suspension of all cycling races until 1 June, a little over three weeks before the event is due to begin in Nice on 27 June.

The French government indicated last week it was looking at ways cycling's biggest race might be able to take place 'behind closed doors' but the feasibility of staging such an event in any form is increasingly questionable as the shut down of professional cycling continues.

Tour de France director Christian Prudhomme told French newspaper L'Equipe his organisation would adapt as necessary to the ongoing fight against the coronavirus.

"I would be lying if I said that we were not working on another hypothesis," he said of the race starting on time.

"The riders must be able to resume training at the end of April for the Tour de France to remain on these dates. But the most important thing by far is the fight against the pandemic.

"We will adapt according to the health situation in the country."

Following talks with representatives of race organisers, teams and riders, the UCI said on Wednesday it was extending its shutdown of racing and working on a revised calendar which would give priority to the three Grand Tours - the Giro d'Italia, Tour de France and Vuelta a Espana - as well as the Monuments, the five biggest one-day races.

"Given the severity of the health situation throughout the world, the UCI and its stakeholders unanimously decided to prolong the suspension of cycling competitions until 1 June 2020, and until further notice," a statement said.

"The UCI also decided that this extension would apply to all cycling disciplines and all categories of riders.

The Giro d'Italia, which had been due to begin on 9 May in Budapest, was among the first races to be postponed, while the status of the Vuelta, scheduled to start in Utrecht on 14 August, remains in the balance.

Of the five Monuments, four - Milan-San Remo, the Tour of Flanders, Paris-Roubaix, and Liege-Bastogne-Liege - have already been postponed while the fifth, the Giro di Lombardia, remains scheduled for 10 October as it stands.