A number of key US envoys have once again extended their stay in Egypt in the face of continuing political deadlock following the ouster of former president Mohamed Morsi.

State news agency MENA reported that on Tuesday Republican senators Lindsey Graham and John McCain will meet with Egypt's interim President Adly Mansour, Defence Minister Abdel-Fattah El-Sisi, Vice President for Foreign Affairs Mohamed ElBaradei, and Prime Minister Hazem El-Beblawi.

The duo will also sit down with a number of representatives of the pro-Morsi National Alliance to Support Legitimacy, as well as other political figures.

Graham and McCain are set to leave early on Wednesday morning.

In addition, US Deputy Secretary of State William Burns has indefinitely extended his stay in Egypt. He had initially been scheduled to leave on Monday and had already announced an extension by one day.

Western and Arab states, unsettled with the violence and deepening turmoil convulsing the Arab world's most populous state, have been working to mediate between Egypt's interim administration and allies of toppled Islamist president Morsi.

Tensions have been running high in Egypt amid government calls for Morsi supporters to end their Cairo sit-ins and return to political negotiations. Morsi's camp has remained defiant in the face of the government's orders and continuing threats by the interior ministry that the sit-ins will be dispersed.