Cairo - An Egyptian court sentenced on Monday a prominent opposition leader widely expected to run against President Abdel-Fattah al-Sisi in next year's elections to three months in prison for offending public morals, his lawyer said.Tarek Hussein said Khaled Ali didn't attend the trial at the misdemeanor court of Cairo's Dokki neighborhood, where he was convicted for making an obscene finger gesture.He said Ali was ordered to pay 1 000 Egyptian pounds (nearly $57) to remain free on bail. The verdict can be appealed, but if confirmed it will prevent him from standing in the 2018 presidential elections.Hussein said the court didn't allow the defense lawyers a closing argument or for them to cross-examine witnesses for the prosecution over disputed video evidence submitted against Ali. Hussein and his team contend the footage was fabricated.The incident allegedly occurred outside a courthouse in January where Ali and other lawyers had just won a landmark case against the government, blocking its attempts to hand over control of two strategic Red Sea islands to Saudi Arabia. The presidency has since ratified the transfer of the islands.Amnesty International called on Egyptian authorities to quash the conviction on the "absurd" charge against Ali, saying it is politically motivated."Khaled Ali's politically motivated conviction today is a clear signal that the Egyptian authorities are intent on eliminating any rival who could stand in the way of President Abdel-Fattah al-Sisi victory in next year's elections," Najia Bounaim of the London-based advocacy group said in a statement.She said the verdict "illustrates the government's ruthless determination to crush dissent to consolidate its power."Ali unsuccessfully contested presidential elections in 2012. He did not run in the 2014 elections which el-Sissi, a general-turned-president, won a year after he led the military's ouster of an Islamist president. He told The Associated Press in February that he was considering running next year. There have since been a series of consultations among liberal and pro-democracy parties on finding a consensus candidate, with Ali a clear front-runner.