Egypt's interim government should release ousted Egyptian president Mohamed Morsi, the US State Department said Friday.
Speaking to reporters, a State Department spokesperson said that the detention of Morsi and his Muslim Brotherhood colleagues were "politically motivated" and that they should all be released.
Egypt's military detained Morsi when it seized power in a coup on July 3. Morsi, who served as Egypt's president for one year but faced unprecedented protests against his rule, has not been seen publicly or heard from since.
Friday marked the first time the Obama administration has called for the deposed leader's release.
Also Friday, tens of thousands of Morsi supporters rallied throughout Egypt, according to the Associated Press.
Many protesters are members of Morsi's Muslim Brotherhood party, but the AP reported more Egyptian flags than Islamic banners waving at the group's Cairo rally.
"We are ready to stay for a month, two months, a year, or even two years," Salafi cleric Safwat Hegazi proclaimed at Cairo's Rabaah al-Adawiya Mosque, where the AP said Morsi loyalists have been congretating for weeks.
The Muslim Brotherhood movement has vowed to keep protesting until he is reinstated, saying democracy is under threat in Egypt, Voice of America said.
According to the BBC, thousands of his supporters were gathering in the east of the capital to call for Morsi's reinstatement.
The military has placed itself strategically throughout the city to ensure rival factions don't mix, and violence doesn't ensue, Al Jazeera reported.
Thousands backing Morsi gathered in Nasr City chanting and calling for Gen. Abdul Fatah al-Sisi, head of the army, to step down from power.
The counter protests are to happen in Tahrir Square and the Presidential Palace for evening prayers.
The Brotherhood has said the removal of Morsi and establishment of an interim government threatens the country's fragile democracy.
Gehad El Haddad, a spokesman for the Brotherhood, said: "We will keep upping the pressure on the military coup by protesting and by having sit-ins and million-man marches every other week.
"We are logistically capable of continuing this hopefully, and the only thing we can do is we stand by our principle and call on the Egyptian people to defend their democracy," Haddad said. "And it's their choice."
However, the opponents whose mass demonstrations led to Morsi's removal by the military last week were expected in huge numbers again in Cairo's Tahrir Square.
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Egypt's interim prime minister has expressed hope that a new government would be sworn in by the end of next week, according to Reuters.
Hazem al-Beblawi said he's searching for two things from an interim government, "efficiency and credibility."
"I don't look at political association," he told Reuters. "If someone is named from (the Brotherhood's) Freedom and Justice Party, if he is qualified for the post he may be considered."
The Egyptian Army is holding Morsi incommunicado at the Republican Guard compound in Cairo where troops killed 53 people, mainly Brotherhood supporters, on Monday.
Four members of the security forces were also killed in the violence, which the military blamed on "terrorists."
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