Josh Huck, a career diplomat who is the embassy's second-ranking official, is expected to take charge of the U.S. Embassy in Athens as chargé d'affaires after the White House asked Ambassador Kimberly Guilfoyle to resign, according to Greek reports.
A permanent replacement is unlikely before the Nov. 3 midterm elections.
The White House made the request Tuesday after reports of improper conduct before and during her posting.
Ms. Guilfoyle said she is stepping aside and denies wrongdoing. No successor has been named.
The outcome of the midterms could shape the timing. Naming and confirming an ambassador is a slow process that can take months, and it may depend on whether Republicans keep control of both chambers of Congress.
The embassy will not be leaderless in the meantime.
Mr. Huck arrived in Athens in August 2025.
He previously served as deputy assistant secretary of state overseeing policy on Southern Europe and the Caucasus and directed the Office of Southern European Affairs, which covers Cyprus, Greece, Malta and Turkey.
He holds degrees from Johns Hopkins University and the International University of Japan and speaks Mandarin, Japanese, Burmese and Bulgarian, the reports said.
Since arriving, he has focused on U.S.-Greek energy cooperation, in particular the Vertical Corridor, a gas route that carries American liquefied natural gas north through Greece to Europe, and efforts to cut the continent's dependence on Russian gas.
Embassy continuity is not new for Athens.
The post had no ambassador for most of 2025, after George Tsunis left in January, and ran under a chargé until Ms. Guilfoyle arrived in November.
The State Department did not immediately comment on the arrangement.