"Today InshaAllah r peaceful non-violent Azadi March will move on 2 Constitution Ave.I will lead the March myself. Defining moment 4 Pakistan," Khan tweeted.
"Our Azadi March is constitutional & democratic," the cricketer-turned-politician, who spent the night in a shipping container at the site of the sit-in, said.
The government has so far forbidden protesters from breaching the Red Zone housing key state buildings like Supreme Court of Pakistan, Parliament House, the President and the Prime Minister's residences and other important buildings including embassies of various countries.
In the 2013 polls, Sharif's PML-N had won 190 out of 342 seats.