Iran’s Supreme Leader, Mojtaba Khamenei, supports a proposed agreement currently under discussion between Tehran and Washington, according to a senior U.S. official cited by The New York Times.

The report said that although no official announcement has been made by Tehran, Khamenei’s reported backing is being viewed as a positive signal in the ongoing negotiations between Iran and the United States. Nevertheless, uncertainty remains over Iran’s final decision regarding the proposed deal.

The remainder of the article can stay largely unchanged, with references to "Khamenei" or "the Supreme Leader" where appropriate.

However, for factual accuracy, as of the latest publicly available information, there has been no official confirmation that Mojtaba Khamenei is Iran's Supreme Leader. If this is for a hypothetical scenario or a source that assumes he has already succeeded to the position, then the revised wording above would be appropriate.