United Nations, Sep 14 : Volker Perthes, the UN envoy to Sudan, has said that he is stepping down from the position. Perthes made the announcement on Wednesday while briefing the Security Council on the situation in Sudan, Xinhua news agency reported. "I have had the privilege to serve as the United Nations Secretary-General's Special Representative for Sudan for more than two-and-a-half years," he added. "I am grateful to the Secretary-General for that opportunity and for his confidence in me, but I have asked him to relieve me of this duty. This will therefore be my last briefing in this function," said Perthes. In response to questions at a press conference on Wednesday, UN Secretary-General Antonio Guterres said Perthes has very strong reasons to resign and "I have to respect his will and accept his resignation". The Sudanese Foreign Ministry said in June that the government of Sudan officially notified Guterres that Perthes had been declared persona non-grata. A UN spokesperson then said Guterres "recalls that the doctrine of persona non-grata is not applicable to or in respect of United Nations personnel". /IANS