Tennis star Maria Sharapova will once again be a UN goodwill ambassador when her doping ban expires in April and she returns to international tennis competition, a UN statement said. The United Nations had suspended Sharapova's role as goodwill ambassador in March after she failed a drug test, putting a hold on a nine-year partnership with the UN Development Programme.Last month, the Russian star's 24-month ban for testing positive for meldonium was cut to 15 months by the Lausanne-based Court of Arbitration for Sport. Sharapova had admitted using meldonium for 10 years to help treat illnesses, a heart issue and a magnesium deficiency.