It was the latest move by the Muslim Brotherhood-led administration to secure freedom for Egyptians jailed for Islamist militancy at home and abroad in the few weeks since President Mohamed Morsi was sworn in.
During his campaign for the presidency, Morsi promised to work for the release of Sheikh Omar Abdel Rahman, the spiritual leader of Al-Gama'a al-Islamiya who is serving a life sentence in the United States for planning attacks in New York.
Analysts doubt he will succeed. Morsi did not raise the case during a July 14 meeting with U.S. Secretary of State Hillary Clinton in Cairo, Clinton said when asked about the issue.
"Seeking the release of Islamist prisoners of some sort or another certainly seems to be one of the early themes of his presidency," said Shadi Hamid of the Brookings Doha Center, saying it appeared to be driven by domestic politics.
Foreign Minister Mohamed Kamel Amr sent a letter to Clinton on Tuesday asking for the release of Tarek El Sawah, the last Egyptian held in Guantanamo, spokesman Amr Roshdy said.
El Sawah has been detained in Guantanamo without trial or proof of crime, the letter said, adding the Egyptian government will appoint an American lawyer specializing in the rights of Guantanamo prisoners to defend him.
Human Rights Watch published a report in 2009 that said El Sawah had been charged with conspiracy and material support for terrorism for allegedly serving as an al Qaeda explosives expert.
Egypt's Foreign Ministry said in its letter the accusation against El Sawah of backing terrorist groups in Afghanistan had been dropped by the American military prosecution in March, but did not mention other charges.
The Muslim Brotherhood renounced violence decades ago. Morsi secured the backing of ultra-orthodox Salafi Islamist parties including Al-Gama'a al-Islamiya to win the election.
Al-Gama'a al-Islamiya waged an armed insurrection against the state in the 1990s but declared a truce in 1997 and published a series of books renouncing violence in 2003.
Since Hosni Mubarak was toppled from power in February 2011, the group has entered mainstream politics, winning seats in parliament.
In another gesture to Al-Gama'a al-Islamiya and Islamic Jihad - the group behind the 1981 assassination of President Anwar Sadat - Morsi has also pardoned at least 17 Islamists jailed in Egypt for militancy during the Mubarak era.
The releases have angered activists credited with igniting the uprising against Mubarak who want Morsi to do more to secure the release of civilians who have been tried by military courts since Mubarak was deposed.
"This is a clear political bias from the president towards particular types of political prisoners," said Samir Ghattas, head of the Middle East Forum, a think-tank. "There are prisoners from the days of the revolution for whom President Morsi has not issued a pardon."