Negotiators for the rival Palestinian factions Hamas and Fatah met today in Cairo to choose a prime minister for the unity government they've agreed to form with the help of Egyptian negotiators. It turns out, however, that that task is too controversial to be carried out in a day. The AP is reporting that talks have broken down and are rescheduled for next week, when the big guns--Palestinian President Mahmoud Abbas of Fatah and Hamas leader Khaled Mashaal (pictured above)--can attend.

Why is choosing a prime minister proving so hard? The AP explains that Hamas sees the current Western-backed prime minister, Salam Fayyad, a "popular moderate," as "too close to the West" while "Fatah believes the U.S.-educated economist is the best candidate to ease concerns that donor money might go to Hamas," which Israel, the U.S., and the E.U. consider a terrorist organization. After today's summit, Hamas officials claimed the two sides had agreed that Fayyad, would step down, but a Fatah official denies that.

As the AP notes, creating a unity government for the West Bank and Gaza Strip is considered a prerequisite for Palestinian statehood. The Palestinians are considering seeking unilateral recognition of a Palestinian state at the United Nations in September, but the European Union joined the U.S. and Israel over the weekend in trying to avoid that scenario. In a letter to U.S. Secretary of State Hillary Clinton, U.N. Secretary-General Ban Ki-moon, and Russian Foreign Minister Sergei Lavrov, the E.U.'s foreign policy chief, Catherine Ashton, called for the Middle East Quartet (the U.S., E.U., U.N., and Russia) to hammer out a framework for a two-state solution based on Israel's 1967 borders with "mutually agreed swaps" and "firm security guarantees"--the principles laid out by President Obama in his Arab Spring speech in May. "This is no time for unilateral moves on either side," Ashton wrote. You can read the full letter here.