DUBAI (Reuters) -The United Arab Emirates’ de facto leader Sheikh Mohammed bin Zayed al-Nahyan was elected president of the Gulf Arab state by a federal supreme council on Saturday, solidifying his rule over the OPEC oil producer and key regional player. He becomes president at a time when the UAE’s long-standing ties with the United States have been strained over perceived U.S. disengagement from its Gulf allies’ security concerns and as Western countries seek support from the region to help isolate Russia over the Ukraine conflict. The council, which groups the rulers of the seven emirates o…