The German-registered team will reveal their goals for 2018 at an official presentation in Berlin on January 4. Last week well-informed Dutch newspaper De Telegraaf and Cyclingnews sources said the Dutchman would return to defend his 2017 victory at the Giro d'Italia.
Today De Telegraaf quoted a team spokesperson as saying: "Tom is going to the Giro for the classification. After the Giro d'Italia we are going to analyse his performance and only then will we decide whether he will also ride the Tour."
The official Giro d'Italia Twitter account also confirmed Dumoulin's presence, writing: "Tom Dumoulin will ride the #Giro101 to defend the Maglia Rosa!".
Team Sunweb also let slip their goals for 2018 in a trailer for their Creating Memories video shows. Graphics previewing the show from the January 4 team presentation said that Coryn Rivera will talk about her Classics ambitions, Dumoulin will talk about defending his Giro d'Italia title in 2018 and Michael Matthews will again target stages at the Tour de France.
The 101st edition of the Giro d'Italia will start in Israel on Friday, May 4 and end in Rome on Sunday, May 27. The Giro d'Italia was voted Best Stage Race in 2017 in the recent Cyclingnews Reader Poll
The Tour de France will begin on July 7, one week later than usual, giving riders an extra week to recover after the Giro d'Italia. However the Vuelta a España is also attracting several big name contenders because it offers excellent preparation for the hilly UCI Road World Championships in Innsbruck, Austria.
Dumoulin revealed he had decided his Grand Tour goals for 2018 at the presentation of the Giro d'Italia route on November 29 but refused to reveal them before the Berlin team presentation. He said a decision on his Grand Tour goals was based on logic.
"I go wherever I think I have the best chance of winning," he told Cyclingnews. "Any course in Italy is tempting for me; I love the country, so it's really hard to say no to the Giro.
"The course is nice, it's a good mix of everything but it's not perfect for me. I would have liked more time trial kilometres but I can understand the race organisers, they want to have an exciting race where anybody can win."
Dumoulin could face Chris Froome (Team Sky) at the Giro d'Italia depending on the outcome of his Adverse Analytical Finding for salbutamol. Also due to target the 2018 Giro d'Italia are Fabio Aru (who joins UAE Team Emirates for 2018), Esteban Chaves and Simon Yates (Mitchelton-Scott) and Miguel Angel Lopez (Astana).
Vincenzo Nibali (Bahrain-Merida), Romain Bardet (AG2R-La Mondiale), Rigoberto Uran (EF Education First-Drapac) and Bauke Mollema (Trek-Segafredo) have all confirmed they will target the Tour de France in 2018.
Dumoulin won the 2017 Giro d'Italia ahead of Nairo Quintana and Vincenzo Nibali in May, claiming two stages en route to overall victory. It was the first Grand Tour victory for the 27-year-old Dutchman and the first Giro d'Italia victory for a rider from the Netherlands.