Egypt's prime minister says the decision to clear two Muslim Brotherhood-led sit-ins is "irreversible."

The announcement by Hazem el-Beblawi on state television Wednesday comes after the presidency said diplomatic efforts to peacefully resolve the standoff between the country's military-backed interim government and the Brotherhood have failed.

Neither announcement said what the interim leadership's next step would be, but hinted that a forceful breakup of the sit-ins may be imminent.

In the past week, authorities have outlined plans to break up two major sit-ins in Cairo by supporters of ousted president Mohammed Morsi. Diplomatic efforts were largely centred on finding a compromise in order to avert the use of force against the sit-ins.

Egypt's presidency said Wednesday that more than 10 days of diplomatic efforts to find a way out of the standoff have failed.

The statement follows a flurry of diplomatic visits by envoys from the United States, the EU and Arab Gulf states to defuse the crisis between the government and Morsi supporters.

The comments from the office of interim President Adly Mansour, who was installed by the military after the July 3 coup that overthrew Morsi, said the mediation efforts have ended and blamed the Brotherhood for the failure to reach a resolution.

"These efforts did not achieve the success that was hoped for, despite full support provided by the Egyptian government," the statement said. "The state of Egypt appreciates the efforts of friendly nations and understands the reasons why they did not achieve their desired objectives, and holds the Muslim Brotherhood full responsibility for the failure of these efforts."

Already more than 250 people have been killed in violence since the military ousted Morsi more than a month ago. His supporters have staged daily protests since.

'A huge mistake'

The presidency's statement was released a day after a visit to Cairo by two U.S. senators who urged the military-backed interim government to release Islamist figures as a gesture to the Brotherhood or risk making "a huge mistake."

Mansour rejected the senators' message, calling it "unacceptable interference in internal politics."

The Brotherhood is demanding Morsi's reinstatement as Egypt's first freely elected president while the new government vows to push ahead with fresh elections early next year.

Before dawn Wednesday, a security official said clashes between supporters of the country's ousted president and residents of Egypt's Mediterranean city of Alexandria have left one person dead and dozens wounded. Residents of the Manshiya neighbourhood were angered by marchers who were chanting against the country's armed forces. It was not immediately clear what sparked the violence.

The official, who spoke anonymously in line with regulations, said 46 people were wounded, including some by gunshot and birdshot, in the violence.