Supporters and opponents of the ousted Egyptian Islamist President Mohammed Morsi are preparing to stage large rallies in Cairo on the first Friday of the fasting month of Ramadan.
Mr Morsi's supporters are gathering in their thousands in the east of the city to call for his reinstatement.
Those whose mass demonstrations led to his removal by the military last week are expected to mass in Tahrir Square.
Dozens of people have died in clashes since Mr Morsi's ousting.
Mr Morsi's Muslim Brotherhood movement may have alienated many people while in office, but many Egyptians are also uneasy at the military's intervention in the country's politics, analysts say, and what is emerging is a battle for public opinion and the middle ground.
On Thursday the US urged Egypt's leadership to stop the new authorities' "arbitrary" arrests of Muslim Brotherhood members, warning against targeting any particular group.
Germany's foreign ministry called for all groups to refrain from violence, while urging the Egyptian authorities to end restrictions on Mr Morsi and allow an international organisation access to him.
UN chief Ban Ki-moon has also warned against the exclusion of any party from the political process.
However, White House spokesman Jay Carney said that the US administration did not believe it should immediately suspend aid to Egypt.
Washington is due to send four F-16 fighter jets to Egypt, but has not publicly confirmed that the delivery will go ahead.
The US administration says it is examining whether the military takeover constitutes a coup - US law prohibits the sending of aid to any country whose elected leader is deposed by a military coup.
Mr Morsi's supporters have been staging mass protests throughout the week near the Presidential Guard barracks in eastern Cairo, where they believed he is being held.
The focal point of the protest is the Rabaa al-Adawiya Mosque, where they are camping out around the clock in their thousands.
Our correspondent says the Brotherhood is not planning any marches but organisers are hoping that a massive turnout will show support snowballing in their favour.
Tens of thousands came for midday prayers outside the mosque despite the heat and the absence of food and drink, in what is expected to be a full day of protests.
Mr Morsi's supporters say they are not seeking confrontation or violence, but given the bitterly polarised situation, with feelings running high on both sides, the potential is always there, correspondents say.
Their opponents are planning rallies for Tahrir Square, including a mass iftar - breaking the fast.
Mr Morsi was removed on 3 July - a year after he was elected - following protests by millions of people across Egypt, and an interim President, Adly Mansour, was installed.
While the new authorities have not specified where Mr Morsi is, a foreign ministry spokesman has said he is in a "safe place" and being treated in a "very dignified manner".
However, reports emerged on Thursday that prosecutors are planning to investigate allegations that Mr Morsi and other Muslim Brotherhood leaders escaped from jail in 2011 with the help of the Palestinian Islamist group Hamas.
The Brotherhood leaders had been arrested two days earlier, in the midst of the revolution that overthrew Hosni Mubarak, and sent to the Wadi Natroun prison, north of Cairo.
Hamas has been accused of sending fighters from Gaza to storm prisons, thereby violating Egyptian security. It denies the accusations.
Dozens of people have died in deadly clashes in the aftermath of Mr Morsi's ousting. On Monday alone more than 50 Morsi loyalists were killed in clashes with the army.
The Muslim Brotherhood's spiritual leader, Mohammed Badie, and nine other senior figures were charged on Wednesday with inciting Monday's violence, despite conflicting accounts of the incident.
Mr Badie's whereabouts are not known.
Mr Mansour has set a timetable for a new constitution and elections, but Mr Morsi's supporters have rejected the plan and some political groups opposed to him say they were not consulted about it.
Meanwhile Hazem al-Beblawi, who Mr Mansour appointed as prime minister on Tuesday, has said he could offer cabinet posts to the Freedom and Justice Party (FJP), the political wing of the Muslim Brotherhood.
The FJP has rejected the offer.