MotoGP title leader Jorge Lorenzo appears open to the possibility of former team-mate Valentino Rossi returning to Yamaha in 2013.

Rossi requested that the wall dividing the Yamaha pits in 2008, due to a difference in tyre manufacturer for Rossi and Lorenzo, remain in place even after MotoGP switched to a single supplier in 2009.

It seemed to sum up the frosty relationship that existed between Lorenzo and Rossi, although the Spaniard - Rossi's toughest ever team-mate - always felt it was unnecessary.

"In the case Valentino joins again Yamaha there will be no wall from my part, of course," said Lorenzo at Assen on Friday. "I always thought it was not necessary and I still believe that."

Lorenzo, world champion during Rossi's injury-interrupted final M1 season in 2010, recently extended his Yamaha contract until the end of 2014.

But the Spaniard stated that Yamaha will decide the identity of his team-mate.

"Valentino is a good rider, he has won a lot of titles and a lot of races," he said. "I think he can still be competitive in MotoGP so he is an interesting rider for Yamaha. Of course there are other riders that could be good for them also, so they will have to decide."

Rossi has taken just two podium finishes since leaving Yamaha for Ducati. The Italian is being linked with a possible return to Honda as well as Yamaha, but insists his objective is to continue with Ducati.

Ben Spies currently occupies the second factory M1 seat, but is just eleventh in the championship.

MotoGP rules announced at Assen on Friday confirmed that each manufacturer is officially limited to four bikes, two official and two satelitte, reducing the chances of Rossi setting up his own team.