Several opposition forces released a statement on Thursday asserting that they would not accept the return of former Mubarak-era officials to power as an alternative to President Morsi and his regime.
"The revolution will not tolerate any opportunists who aim for personal gain," the statement read, adding "We will not allow for the return of Mubarak [officials] or the military."
The opposition forces, which include the April 6 Youth Movement, the Revolutionary Socialists, and the Strong Egypt Party lead by Abdel-Moneim Abul-Fotouh, said that the January 25 Revolution did not end when the Egyptian people brought down Mubarak in 2011.
"The struggle did not stop because we continue to face the same regime, even if it has a military or a religious facade," the statement read.
The Supreme Council of the Armed Forces (SCAF), headed by former field marshal Mohamed Hussein Tantawi, assumed power between February 2011 and June 2012 after former president Hosni Mubarak's ouster. SCAF rule was followed by the election of Mohamed Morsi, who hails from the Muslim Brotherhood, to the presidency.
Egypt is anticipating nationwide protests on Sunday 30 June, which will call for Morsi to step down in addition to early presidential elections.
Supporters of the president, particularly the Muslim Brotherhood and its Freedom and Justice Party (FJP), assert Morsi's "constitutional legitimacy" to continue his term as president. They claim that opposition protests are supported by ex-Mubarak officials who want to reclaim power.
The opposition statement described Sunday's protests as a "completion of the revolution and the fulfillment of its goals, from which the president strayed."
"We commit to peaceful and popular means to achieve our goals," the statement concluded.
A number of public figures also signed the statement, including ex-MP Amr Hamzawy, writer Alaa El-Aswany, political scientist Rabab El-Mahdi, and former presidential contender Khaled Ali, among others.
Islamist forces are holding an open-ended sit-in at Rabaa Al-Adawiya Mosque in Cairo's Nasr City on Friday in support of Morsi. They held a similar rally last week, which numbered in the hundreds of thousands.
Tensions have been building between opponents and supporters of the president after clashes in several governorates – including Daqahliya, Sharqiya and Zagazig – left three dead and scores injured in the past week.
A three-hour speech by the president on Wednesday night offered limited concessions and called for national reconciliation but was not well-received by the opposition.