By January 1827 Mehmed Ali was already contemplating rebellion against the Sultan

Evidence

His position as vali, however, weighed heavily on him and there is some evidence that suggests that as early as that time he was considering what it would take to rebel against the authority of the Sultan. In January 1827, for example, the Pasha had a long conversation with Salt and touched on the difficulty of any Pasha succeeding in rendering himself independent of the Sultan. — Khaled Fahmy, All the Pasha_s Men_ Mehmed Ali, his…, 233