Chief Palestinian negotiator Saeb Erekat said on Friday he was suffering "difficult" symptoms after contracting coronavirus, but that things were "under control".
Erekat, 65, a lawmaker from Jericho in the occupied West Bank, said on Twitter that he was in isolation and receiving medical treatment at home one day after he confirmed that he had caught the virus.
He has cancelled all meetings and appointments. There is heightened concern over his vulnerability because he underwent a lung transplant in the United States in 2017.
In tweets on Friday, Erekat said he was experiencing "difficult symptoms resulting from my lack of immunity as a result of lung transplantation". But he thanked well-wishers and said "things are under control, thank God".
Erekat is secretary general of the Palestine Liberation Organization and is one of the youngest members of the PLO's most senior bodies, the Executive Committee.
A member of Fatah, the most powerful faction within the PLO, he has been one of the most high-profile faces of the Palestinian leadership for decades, especially to international audiences.
A veteran negotiator and spokesman, he is one of the most senior advisers to Palestinian President Mahmoud Abbas, and also served in senior positions under Abbas' predecessor, Yasser Arafat.
His negotiating days date back to the earliest public negotiations with Israel in 1991 at the Madrid Conference during the presidency of George H.W. Bush, when Erekat was part of the PLO team that also included Hanan Ashrawi.