It has been officially confirmed that reigning 250cc world champion Marco Simoncelli will ride for Gresini Honda in the 2010 MotoGP World Championship.

During the Grand Prix of Catalunya it was rumoured that Simoncelli had signed an agreement with HRC that would see the Italian make his MotoGP debut with Gresini in 2010.

Those rumours were publically denied, but an announcement by the Gresini team on the eve of this weekend's Dutch TT confirmed the 22-year-old as the first new rider on the 2010 MotoGP grid.

A new rule prevents rookies riding for a factory MotoGP team, except Suzuki, but Simoncelli could still potentially enjoy factory HRC support and equipment within the Gresini structure.

Upon making the announcement, Fausto Gresini also revealed that San Carlo has signed a new title sponsorship agreement with his team.

"We're extremely happy to be able to make this important announcement: renewing our agreement with San Carlo, who have shown great belief in us and continue to support our targets for next year, and the agreement with Marco Simoncelli to race with us in MotoGP," began Gresini.

"Marco has that determination and character that we want from a rider as part of his DNA and we are sure we can look ahead to exciting times with him. Marco has shown over the past couple of years that he has the ability to be a major force in the premier class, as well as being a great communicator."

It had been suggested that Simoncelli would sign directly for Honda and then be placed at Gresini by HRC, but Gresini's comments seemed to indicate that the team had taken the initiative.

"We have established a good feeling with [Marco] already and that facilitated negotiations over a contract that we have signed for 2010," he said. "Also, Honda rates Simoncelli highly and believes he is a rider with great potential for the future, so Honda is very pleased that we are welcoming Simoncelli next season.

"Today is an important day for San Carlo and ourselves, and as we wait in expectation of great things together in the future, we wish Marco all the best in his bid to fight until the end and successfully defend his 250 title."

By the end of this season, Simoncelli will have spent seven seasons in the lower grand prix classes, with three years in 125 being followed by four in 250.

Prior to 2007, the Gilera rider was best known for his extravagant hair style rather than race results, with only two 125cc victories to his credit and not even a podium to show for his first two seasons in the quarter-litre class.

But Simoncelli was transformed during 2008, fighting back from two DNFs in the first two rounds to claim twelve podiums from the remaining 14 races - including his first six 250GP victories - to wrap up his first world title.

The offer of a satellite Ducati MotoGP ride was politely declined, but Simoncelli's 2009 title defence got off to a nightmare start when he broke his wrist just before the start of the season.

After six rounds, Simoncelli has scored three podiums - including one win - but failed to score in three other rounds and sits fifth in the championship, 47 points behind arch-rival Alvaro Bautista. Bautista is also expected to move to MotoGP next year.

After a season with Gresini, Simoncelli - a friend of Valentino Rossi - will presumably have his eye on a place at the factory Repsol Honda squad for 2011.

Gresini Honda is currently experiencing a difficult season with Toni Elias and Alex de Angelis. de Angelis is 13th in the championship with 25 out of a possible 150 points while Elias, who has a factory spec RCV, is one place and two points behind the San Marinese.

At least one rider will now leave the team at the end of the year, and possibly both.