Asked if the much-hyped reigning Formula 2 champion and Ferrari junior Leclerc would make a good teammate, Vettel said in Monaco: "I don't sign who sits next to me. You should probably ask Maurizio (Arrivabene).
"But I don't see why not. I think the hype is absolutely justified. If there's no hype around him, then I don't understand who should be hyped because if you walk through all the categories like that, then you belong here," he added.
As for the Hamilton rumours, the Mercedes driver is yet to sign his delayed contract but admits he doesn't "anticipate" being Vettel's next teammate.
"He (Vettel) has a veto so that wouldn't happen," Hamilton added.
Vettel denies that, but he does admit to Italy's La Gazzetta dello Sport that he is happy alongside Raikkonen.
"We share the same values and have a great respect for one another," said the German.
"What I like most is that I can be myself. There are no mind games as there are with other teammates, and I think that's a win for Ferrari.
"There is no controversy, no distraction, no politics."
But when asked if he thinks Raikkonen will stay in 2019, Vettel answered: "I don't know. It doesn't depend on me.
"One day, Kimi could decide that he doesn't need it any more. But if you ask the question 'Would I rather drive with Kimi than another driver?' then the answer is yes."