CAIRO — Egypt's highest security body warned on Sunday that the clock is ticking in the search for a peaceful end to the standoff over sit-ins by ousted president Mohamed Morsi's supporters, suggesting that authorities will break up the vigils unless ongoing mediation efforts produce results soon. The US and EU are trying to mediate a peaceful resolution to the standoff to avoid a repeat of deadly clashes between Morsi's supporters and security forces that have killed at least 250 people since the army shunted Morsi aside. But Egypt's National Defense Council said the search for a peaceful resolution is not open-ended, and that a negotiated end would not shield what it called “law-breakers” and others who incite against the state from legal proceedings. The NDC is led by the interim president. It includes Defense Minister Gen. Abdel-Fatah El-Sissi, who led the July 3 coup, as well as other top ministers. Sunday's statement by the National Defense Council is the latest warning to the pro-Morsi protesters. Egypt's Interior Ministry, which is in charge of the police, called on them on Saturday to abandon their protest camps, while a senior US diplomat met with officials on both sides of the country's political divide. US Deputy Secretary of State William Burns extended his visit to Cairo by one day so he could meet El-Sissi and the country's prime minister on Sunday, an Egyptian Foreign Ministry official said. A member of the pro-Morsi delegation that met Saturday with Burns said the four delegates also would hold another round of talks with the U.S. diplomat on Sunday. At the core of discussions is the political future of the Muslim Brotherhood, the Islamist group from which Morsi hails, and its Islamist allies. The Brotherhood says it is looking for concessions before beginning talks with the new, military-backed administration. These measures could include releasing detained Brotherhood leaders, unfreezing the group's assets, lifting a ban on Islamist TV stations loyal to Morsi and reigning in the use of force against its protesters. — AP