Vasseur was responding to ongoing speculation about Leclerc's growing frustration at Ferrari, amid suggestions that he might look elsewhere at the end of his current contract.
The Frenchman stressed that successful team projects are always built around the contribution of a driver, citing examples that included the Michael Schumacher era at Maranello, and insisted that Leclerc is fully immersed in the current rebuilding programme.
"He's clearly part of the project, that means he is not a spectator of this," said Vasseur. "He is involved in the development of the team, he is part of the development, because he's developing himself.
"He is a performance contributor on track and out of the track. And as long as he will play this role, we are on a good path.
"It's true in every single team that you are always building a team around the driver. If you ever look over the last 20 years or even more, all the successful top stories in F1 took time. But it was always a team built around someone, a driver. It was true with Lewis [Hamilton] at Mercedes.
"And it was true before with Michael at Ferrari, it was true with [Fernando] Alonso at Renault, it was true everywhere. You can find tonnes of examples.
"For sure that Charles is an important pillar of the performance, and he has to play the role in the car, outside of the car, to be a performance contributor. And he's fully supportive of this part of the job. And I'm really convinced that it's also a personal commitment from himself."
Vasseur stressed that he wanted his drivers to be frustrated if things are not going well, as it was a sign of their hunger for more.
"Frustration is good," he said. "I would be very upset if they were happy with the current situation. But he two times on the first row. We had the DNF on the first one, he got the penalty on the second one.
"Melbourne was not the best weekend of his life, for sure that after three races that if he's not frustrated in the situation, it's a drama and he has to stop.
"I like it. And honestly, we had the discussion and the frustration for me probably is positive. We need to understand what we did well and wrong. And I think we had the discussion together.
"And it's how we can improve. But you can't blame Charles, or feel that Charles was disappointed."
Asked if he had already started talking to Leclerc about a longer-term commitment, he said: "We'll do it in the course of the season. And he's under contract with us for more than one year now, and we'll have time to discuss it, and I'm not scared at all. And I think it's not the right moment to do it."
Sainz penalty
Vasseur also said that the team pursued the right of review request over Carlos Sainz's penalty in the Australian GP as a show of support for the Spanish driver.
The stewards decided that Ferrari's submission did not meet the required standards for presenting new evidence, and thus the penalty remained in place.
"The story of Melbourne, I think every single incident is different, and it's very difficult to say okay, this is the right decision or not," said Vasseur.
"I think the frustration came from the situation, but to give a penalty without hearings when you know that you will restart for a lap behind the safety car, you give five seconds, so it's like a disqualification. You know before that it's a disqualification.
"And the frustration came also probably from the fact that we had other incidents in the same corner with Gasly/Ocon or Sergeant/De Vries, and the treatment was a bit different.
"I don't want to make any comments, but I think that it was important for us to support Carlos, to go to the FIA, to discuss with them, to understand their point of view on this.
"Now the incident is behind us. And we have to look forward and be focused on Baku."
Vasseur admitted that the whole episode had been tough on Sainz.
"I think it was a difficult one for Carlos because he did a very good race if you have a look.
"He was a bit unlucky with the pitstop just before the red flag and he had to do an extra pitstop. And then he came back, he overtook five or six cars, he was catching up - I think it Alonso/Lewis.
"The pace was there, and to get the penalty in the last lap it was a bit harsh and psychologically very harsh."
