MotoGP World Champion Jorge Lorenzo said he 'needed a new challenge' as the Movistar Yamaha rider reflected on his decision to join Ducati at the end of this season.

The three-time premier class champion has signed a two-year deal with the Italian manufacturer for 2017 and 2018, but for now Lorenzo remains totally focused on trying to retain his crown as he prepares for the fourth round of the championship this weekend at Jerez in Spain.

"As you all know next season I won't be with Yamaha. I felt I needed a change, a new challenge in my career, set new goals for me to try to achieve and keep my level of ambition at the maximum," Lorenzo said.

"I have only words of gratitude to the Yamaha family because of all the moments we lived through together. I achieved much more than I'd ever dreamt.

"What will happen in the future is unpredictable but from here on I just want to enjoy these 15 races that I have left with Yamaha to try to ratify the World Championship. This is right now my only target."

Lorenzo began a four-race winning streak at Jerez last year to ignite his title challenge and boasts an excellent record at the Spanish circuit, where he won twice in the 250cc class in 2006 and 2007 before chalking up three MotoGP successes in 2010, 2011 and 2015.

"Jerez is one of my favourite circuits in the world because of the special lay-out of the track and the atmosphere and the people hugging us from the grandstands," he said.

"Last season we kicked off with a good set of four victories in Jerez after a difficult start so hopefully this year we can repeat such a great result."

Lorenzo is currently second in the points standing, 21 points behind Repsol Honda's Marc Marquez.