Toto Wolff has named more candidates as speculation about the Mercedes driver lineup of the future ramps up.
Mercedes wants Hamilton to stay, but the British driver appears to be playing hardball with conditions including contract length and price.
"We want Hamilton to stay with us until 2030," team boss Wolff is quoted as saying by El Mundo Deportivo.
"But in formula one everything is possible and I don't think you'd find a single driver who doesn't want to become champion with Ferrari. But for now Lewis is with us and I hope at least until 2020."
Wolff referred to Mercedes junior Ocon, who currently drives for Force India, as his "little treasure".
"I've known him for a long time and his progress from year to year is very visible," he said.
"Another excellent driver is Carlos Sainz Jr, and if he shows up well next to Nico Hulkenberg then all of the teams will be interested in him.
"We wanted to see Carlos with us and I even met with his father, but they are in the Red Bull programme. But we maintain excellent relations."
Mercedes trail leaders Ferrari by 10 points following the first two races of 2018.