Greek Prime Minister Alexis Tsipras told U.S. Treasury Secretary Jack Lew that a cash-for-reform deal to keep Greece in the euro zone would need the commitment of all sides, a Greek official said, ahead of a crucial summit of euro zone leaders on Sunday. Tsipras told Lew in a telephone conversation that Greece has shown its is willing to reach an agreement, the official said. "For an agreement to be viable it must respect fundamentally the Greek people and everything they have endured over the last five years," Tsipras told Lew, according to the official.