Yamaha expects Rossi to sign deal for 2019

Rossi is yet to extend his existing deal, which will ends this year, and his plan is to wait until after the first few races of the year before signing a new contract.

Jarvis said that even though Rossi is highly likely to continue for at least another year, nothing is done yet.

"I can assure you that nothing is done at the moment but I imagine it won't be too long until Valentino's situation is clarified and I fully expect him to be with us again on the grid next year," he said.

"[This week] we were actually in Manila in the Philippines for a promotional event and Valentino explained to the media there that right now he definitely has the intention and desire to continue.

"It is not yet clear whether he may decide to do a one-year contract or perhaps a two-year contract.

"We're in close contact, we talked to each other already and we decided that we'd like to see a few tests at least under the belt before making a decision, maybe a few races.

"It is difficult to say [when he signs the contract], I think these three tests are important, obviously we've done one and Valentino is feeling comfortably straight away.

"We haven't set ourselves a timeframe at the moment."

Marquez: Rossi at 39 'impressive'

Reigning champion Marc Marquez has expressed his admiration for Rossi's ability to stay motivated and competitive at the age of 39, something "all riders want to do".

"It is something really impressive what Valentino is doing," he said.

"With [turning] 39 years old [today], it is something all the riders want to do because in the end, keeping the motivation, keeping the level during all those years, nobody did in the past.

"He is able every season to improve to keep the motivation, it is impressive.

Marquez, who will turn 25 one day after Rossi's birthday, jokingly added: "We hope that he doesn't improve more and more because he is already very fast."