Ayaz Sadiq, presiding over the assembly session in the absence of the ruling party members and its designated speakers, said nomination papers for candidates should be filed by 11 am local time (06:00 GMT) on Sunday.
Khan, 69, has been deposed by a no-confidence vote in parliament, days after he blocked a similar attempt.
The passing of the motion on Saturday came after the country’s Supreme Court ruled the cricket star turned politician acted unconstitutionally in previously blocking the process and dissolving parliament.
The no-confidence motion, which required 172 votes in the 342-seat parliament to pass, was supported by 174 politicians.
ZZ/PR