Prominent opposition figure Mohammed ElBaradei on Sunday urged Egyptians to join a protest campaign demanding President Mohammed Morsi's ouster, dpa reported.
The Tamarod, or Rebellion, campaign aims to gather 15 million signatures, beating the 13.2 million votes that brought Morsi, of the powerful Muslim Brotherhood, to victory in June 2012.
"I call on every Egyptian to sign petitions by Tamarod in order to regain our revolution," ElBaradei posted on Twitter.
The grassroots campaign is gathering the signatures to withdraw confidence from Morsi and push for early presidential polls.
Its activists expect to reach the targeted figure before June 30, when Morsi completes his first year in office.
ElBaradei, a Nobel Peace Prize winner, is a vociferous critic of Morsi and the Muslim Brotherhood.
"This is a failing and oppressive regime that is killing the spirit of the revolution," ElBaradei wrote, referring to the 2011 uprising that toppled president Hosny Mubarak and paved the way for Morsi's election as president.
Former diplomat ElBaradei is a leading member of the opposition National Salvation Front, which backs the calls for early presidential polls.
In an interview published Friday, Morsi, Egypt's first democratically elected president, rejected these calls as "absurd and illegal." His term ends in 2016.
The mainly secular opposition plans to hold mass protests on June 30 against what it says is Morsi's misrule of the country.
There have been deadly clashes between backers and opponents of Morsi in recent months.