International envoys have extended their visit to Cairo as efforts intensify to find a peaceful way out of the crisis sparked by the Egyptian military's overthrow of Islamist president Mohamed Morsi.
US Deputy Secretary of State William Burns met the No. 2 of Morsi's Muslim Brotherhood movement, Khairat al-Shater, in prison, the official MENA news agency said on Monday.
The report said Burns was accompanied by EU envoy Bernardino Leon and top diplomats of Qatar and the United Arab Emirates during the visit to Shater at Cairo's high security prison in Tora.
Burns and Leon were due to fly out on Sunday night but extended their stay, an airport source said.
The powerful Shater, one of the main financiers of the Muslim Brotherhood, is due to face trial on August 25 along with senior Brotherhood leader Rashad Bayoumi and Brotherhood Supreme Guide Mohammed Badie, who is currently in hiding.
The three are accused of inciting the killing of protesters during clashes outside the Brotherhood headquarters in Cairo in June.
Morsi himself has been formally remanded in custody on suspicion of offences committed when he escaped from prison during the 2011 revolt that toppled former president Hosni Mubarak.
Burns had already met army chief Abdel Fattah al-Sisi amid intense efforts to mediate a solution to the crisis pitting Morsi loyalists and the army-backed interim leadership.
Days of heated diplomatic activity in Cairo have seen visits by Burns, EU foreign policy chief Catherine Ashton, Arab diplomats and an African Union delegation.
Supporters of Morsi - Egypt's first freely elected president - see his ouster by the military as a violation of democracy and insist on nothing short of reinstatement.
The interim leaders however say there is no turning back on the army-drafted roadmap announced after Morsi's ousting on July 3 and which provides for new elections in 2014.
Both the interior ministry and the army have repeatedly called on pro-Morsi protesters to lift their sit-ins which have paralysed parts of the capital and increased divisions in the country.
Authorities have promised Morsi loyalists a safe exit and said an end to their protests would allow the Muslim Brotherhood to return to political life.
Burns had met with members of the Brotherhood's political arm, which later stressed its continued commitment to "legitimacy, which stipulates the return of the president, the constitution and the Shura Council," or upper house of parliament.
The Islamists' declaration suggested Burns had failed to shift their position.
"We affirm our welcome of any political solutions proposed on the basis of constitutional legitimacy and rejection of the coup," said the Freedom and Justice Party statement.
During his visit, the US envoy sat down with Foreign Minister Nabil Fahmy in a bid to broker a compromise as Washington kept up the pressure from afar, with Defence Secretary Chuck Hagel urging Sisi to support an "inclusive political process", the Pentagon said.
