Egypt crisis: McCain and Graham to join diplomatic talks
US senators John McCain and Lindsey Graham are due to arrive in Cairo as diplomatic efforts to end Egypt's political crisis intensify.
US and EU envoys have been meeting officials from the military-backed government and supporters of ousted President Mohammed Morsi.
Their talks took place amid mounting tension over plans to break up two mass sit-ins by Morsi loyalists in Cairo.
A government helicopter dropped leaflets urging people to leave.
The pamphlets, which were dropped over the Rabaa al-Adawiya square, pledged protesters would face no action if they had not committed a crime whilst demonstrating.
More than 100 Morsi supporters have been killed in clashes since the president was overthrown by the military on 3 July.
Meanwhile a court in Cairo said it would start the trial of Muslim Brotherhood leader Mohammed Badie and two of his deputies on 25 August.
Mr Badie and several other senior Brotherhood figures were arrested on charges of inciting violence and complicity in the deaths of anti-Morsi demonstrators during rallies in July.
A Brotherhood spokesman rejected the charges last month as "nothing more than an attempt by the police state to dismantle" the protests.
Mr McCain and Mr Graham are expected to land in the Egyptian capital on Monday evening for two days of negotiations.
Over the weekend, US deputy secretary of state, William Burns, already held separate talks with members of Mr Morsi's Muslim Brotherhood and the Egyptian Foreign Minister, Nabil Fahmy.
The European Union's envoy, Bernardino Leon, also joined the meeting with Mr Fahmy.
Few official details have been given, but the hope is clearly to prevent further violence and bloodshed, correspondents say.
The foreign ministers of Qatar and the United Arab Emirates are also involved in the diplomatic push, and are reported to have visited a Muslim Brotherhood leader.
Meanwhile further talks took place between army chief Gen Abdul Fattah al-Sisi and a prominent group of Islamic clerics.
According to an army statement, Gen al-Sisi told the clerics a peaceful solution could be reached if all sides rejected violence.
However, the preachers were heavily criticised by Morsi loyalists for taking part in the meeting; they say nothing short of Mr Morsi's reinstatement will end their protests.
On Saturday, the interior ministry renewed its call for the demonstrations to end peacefully, and said this would allow the Muslim Brotherhood to return to a role in the democratic political process.
Thousands of Morsi supporters have been defying warnings from the authorities to abandon the sit-ins in Cairo at Nahda Square and outside the Rabaa al-Adawiya mosque, in the east of the capital.
The protesters and their families have been camping there for weeks, demanding the ousted president's reinstatement.