Teams will be forced to race Milan-San Remo with just six riders due to a last-minute change.
The 300km-long race is scheduled for Saturday (August 8) after being delayed from its usual spring spot in March.
But as the UCI tries to fit most of the suspended 2020 calendar into just four months, race organisers are trying to offer places to as many teams as possible.
RCS Sport, organiser of Milan-San Remo, applied to the UCI to allow two more smaller teams to race the 2020 edition, with the governing body approving the request but only if every other team dropped a rider to reduce the size of the peloton.
Italian ProTeams Androni Giocattoli-Sidermec and Bardiani CSF Faizanè have now been invited to the race, as they join four other Wild Card teams, two ProTeams who qualified by ranking and all 19 WorldTour outfits.
Director of cycling at RCS Sport, Mauro Vegni said: “The organisation had already asked the UCI, at this particular moment where there is a need to have as many teams and riders as possible participating, to be able to invite two other teams without reducing the number of riders per team. The UCI rejected the request because this would have meant exceeding the maximum limit of riders in the race allowed by the regulation.”
Under UCI rules, the current number of riders allowed in a peloton is 176.
But if all 27 teams compete with the usual seven-rider squads, the Milan-San Remo bunch would be stretched to 189 riders.
By reducing each team by one rider, instead there will be 162 athletes lining up next month.
When announcing the redesigned WorldTour calendar in May, the UCI said that team sizes for one-day races will be six or seven (rather than the usual compulsory seven). This allows teams to spread their riders more thinly across the packed calendar.
But the decision to reduce the number of riders from seven to six at Milan-San Remo, which came 10 days before the race, has been criticised by team boss Richard Plugge.
The Jumbo-Visma principal said: “Irresponsible and ridiculous decision. The fact that this request is granted is incomprehensible for our governance less than 14 days before the start.”
In 2018, the UC reduced team sizes in all international road races in order to improve rider safety.
Before the changes Milan-San Remo, the longest race on the cycling coming in at 299km this season, had a peloton of more than 200 riders.