International mediators have expressed fears attempts to solve Egypt's crisis may fail, with one U.S. senator warning it could be "days from bloodshed", BBC News reported.

John McCain and fellow senator Lindsey Graham urged the military-backed government to free political prisoners. They also urged talks with the Muslim Brotherhood of Mohammed Morsi, who was ousted by the military on July 3.

But acting President Adly Mansour warned against "unacceptable interference in internal affairs".

Envoys from the European Union, Qatar and the United Arab Emirates are also in the country trying to resolve the crisis. Fears are growing that the army will move in to break up two pro-Morsi sit-ins in Cairo, triggering further violence and bloodshed.

Egypt has been in turmoil since Morsi - Egypt's first freely elected president - was overthrown last month following mass demonstrations against him. He is being detained at an undisclosed location.

The two U.S. senators held talks on Tuesday, Aug 6, with interim Vice-President Mohamed ElBaradei, Prime Minister Hazem Beblawi, and the head of the armed forces, Gen Abdul Fattah al-Sisi.

They also met members of the Brotherhood's political wing, the Freedom and Justice Party (FJP).

McCain later told U.S. broadcaster CBS that the unrest could turn into "all-out bloodshed" in coming days if efforts to find a political solution failed.

"Oh my God, I didn't know it was this bad," he said. "These folks are just days or weeks away from all-out bloodshed. There is only one way to bring about a peaceful Egypt and that is the process of negotiation and reconciliation between the major players."

Graham added: "I'll go one step further. I think it's going to fail if something doesn't change."

A leading member of the Muslim Brotherhood also rejected the U.S. senators' statements. Hassan el-Prince said the U.S. was trying "to jump out of the sinking boat of the coup leaders".