Khan had already been suspended on June 8 by the ICC's governing body, prolonging a crisis at the war crimes court, which is also under US sanctions over investigations into the United States and Israel.
The Bar Standards Board said on Friday that the suspension, effective immediately, would be considered by a panel at a hearing within four weeks.
Khan, 56, denies the allegations against him.
His supporters have suggested that he has become a political target for seeking arrest warrants for Israeli officials over Israel's conduct in its war in Gaza.
The ICC's 125 member states will vote on his fate at a special session of its governing body on July 24.
The ICC, the world's first permanent war crimes court, opened in 2002 to prosecute individuals for war crimes, crimes against humanity and genocide committed by nationals of member states or on the territory of its members.
The US is not an ICC member and has imposed sanctions on 11 ICC judges and prosecutors, including Khan, for issuing arrest warrants against Israeli Prime Minister Benjamin Netanyahu and former defence minister Yoav Gallant, and for a past probe into US troops in Afghanistan.
Washington has threatened more sanctions against the institution.
After the allegations against Khan emerged in 2024, it commissioned an external UN investigation.
In May 2025, Khan went on voluntary leave and his two deputies assumed his duties.
A summary seen by Reuters said the confidential 18-month inquiry had found a "factual basis" for the allegations, made by a female aide, that he had had a non-consensual sexual relationship with a younger staff member.
Khan maintains he did nothing wrong and has said he will take all necessary steps to challenge his suspension at the ICC.
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