Arabic media had reported earlier Thursday that de Mistura had handed in his resignation for personal reasons.
The 69-year-old was named to the post in July 2014, charged with the daunting task of trying to find a peaceful resolution to the conflict that has torn Syria apart since 2011, killing 300,000 people.
Two other special envoys had previously held the post before resigning: former UN secretary-general Kofi Annan, and former Algerian foreign minister Lakhdar Brahimi.
De Mistura, a Swedish-Italian career diplomat, told Swiss public TV network RTS last month that he had no plans to quit the job, despite the difficulty of the task.
"If I did it, it would only be if I thought there was no use for our work and if my family asked it of me," he said.
"My conscience tells me I must support the Syrians, but no one is indispensible," he added.
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The 69-year-old was named to the post in July 2014, charged with the daunting task of trying to find a peaceful resolution to the conflict that has torn Syria apart since 2011, killing 300,000 people.
Two other special envoys had previously held the post before resigning: former UN secretary-general Kofi Annan, and former Algerian foreign minister Lakhdar Brahimi.
De Mistura, a Swedish-Italian career diplomat, told Swiss public TV network RTS last month that he had no plans to quit the job, despite the difficulty of the task.
"If I did it, it would only be if I thought there was no use for our work and if my family asked it of me," he said.
"My conscience tells me I must support the Syrians, but no one is indispensible," he added.
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