SANAA - A UN envoy said on Tuesday that Yemeni President Ali Abdullah Saleh is preparing to sign an agreement with his opponents to hand over his powers - although he has already backed out three times from such a deal at the last minute."We have an agreement. We're working out the signing," United Nations envoy Jamal Benomar, who has been shuttling between the two sides, told reporters in Sanaa.Under a plan crafted by Yemen's six Gulf Arab neighbors, Saleh would transfer his powers to his deputy, Abd-Rabbu Mansour Hadi, ahead of an early election.However, Saleh has repeatedly failed to sign the deal, which aims to end months of protests that have paralyzed the country.Officials from an alliance of opposition parties and a source in Saleh's ruling General People's Congress said on Monday that a deal had been reached, and that the accord would be signed on Tuesday.Benomar was expected to hold a news conference later in the day on the accord.Under the accord, Saleh would keep the title of president after handing all of his powers to Hadi, who will form a new national unity government with the opposition and call an early presidential election within three months.Opposition officials said that the signing of the accord was due to take place on Tuesday and a ceremony would be held later in the Saudi capital Riyadh. More than 10 months of protests aimed at ending Saleh's 33-year rule have paralyzed Yemen. The renewal of conflict between Islamist militants and separatists during the political deadlock has raised the prospect of chaos on the borders of Saudi Arabia, the world's largest oil exporter.Those fears are shared by Saleh's former US backers, who made him a cornerstone of their campaign against al-Qaida, and have brokered negotiations over implementing the Gulf plan.