Brazils antitrust watchdog has given Telefonica 18 months to comply with a ruling to loosen its grip on the Brazilian mobile market, sources said, time which may help the Spanish group ward off a growing rebellion over its strategy. Brazilian competition regulator Cade decided this month that Telefonica must sell a stake in TIM Participacoes, the local wireless unit of Telecom Italia, or seek a new partner for its Vivo mobile phone business. Vivo is the largest mobile operator in Brazil market and TIM is the second-biggest. The regulator did not say at the time how soon Telefonica must comply with the demand.