Italian rider Vincenzo Nibali has broken his wrist in training to put his race program in doubt, his Team Trek Segafredo revealed on Wednesday.

The Sicilian was transported to hospital in Lugano, Switzerland, where he resides, after a fall ahead of next week's Tour of the Alps.

"Unfortunately Vincenzo Nibali fell this morning during training and hit his right wrist," his team said in a statement.

"Clinical exams have revealed a compound fracture of the radius of the right wrist.

"An osteosynthesis surgery has been scheduled for tomorrow (Thursday) to reduce the fracture.

"After this it will be possible to consider the recovery and Vincenzo's participation at the Giro."

Nibali won the Giro in 2013 and 2016.

This year's race runs from May 8 to 30.

Nibali had just returned from training in Tenerife and had been due to compete in the five-day Tour of the Alps, formerly the 'Giro del Trentino' between Austria and northern Italy, which he has won twice.

The 36-year-old former Tour de France and Vuelta a España winner was also due to compete in the Liege-Bastogne-Liege one-day classic on April 25.